A systematic review of maternal obesity and breastfeeding intention, initiation and duration

  • Lisa H Amir1Email author and

    Affiliated with

    • Susan Donath2, 3

      Affiliated with

      BMC Pregnancy and Childbirth20077:9

      DOI: 10.1186/1471-2393-7-9

      Received: 21 February 2007

      Accepted: 04 July 2007

      Published: 04 July 2007

      Abstract

      Background

      Breastfeeding behaviour is multifactorial, and a wide range of socio-cultural and physiological variables impact on a woman's decision and ability to breastfeed successfully. An association has been reported between maternal obesity and low breastfeeding rates. This is of public health concern because obesity is rising in women of reproductive age and the apparent association with increased artificial feeding will lead to a greater risk of obesity in children. The aim of this paper is to examine the relationship between maternal overweight and obesity and breastfeeding intention and initiation and duration.

      Methods

      A systematic review was conducted in January and February 2007, using the following databases: Medline, CINAHL and the Australian Breastfeeding Association's Lactation Resource Centre. Studies which have examined maternal obesity and infant feeding intention, initiation, duration and delayed onset of lactation were tabulated and summarised.

      Results

      Studies have found that obese women plan to breastfeed for a shorter period than normal weight women and are less likely to initiate breastfeeding. Of the four studies that examined onset of lactation, three reported a significant relationship between obesity and delayed lactogenesis. Fifteen studies, conducted in the USA, Australia, Denmark, Kuwait and Russia, have examined maternal obesity and duration of breastfeeding. The majority of large studies found that obese women breastfed for a shorter duration than normal weight women, even after adjusting for possible confounding factors.

      Conclusion

      There is evidence from epidemiological studies that overweight and obese women are less likely to breastfeed than normal weight women. The reasons may be biological or they may be psychological, behavioral and/or cultural. We urgently need qualitative studies from women's perspective to help us understand women in this situation and their infant feeding decisions and behaviour.

      Background

      Infants not breastfed have increased risks of ill-health – both short- (e.g. gastrointestinal infections [1]) and long-term (such as diabetes [2]). Recent systematic reviews have shown a dose-dependent association between longer duration of breastfeeding and decrease in the risk of overweight in later life [3, 4]. Looking at the population impact, it has been estimated that 13,639 cases of obesity (95%CI 7,838, 19,308) could be prevented in England and Wales over 9 years if all infants were breastfed for at least three months [5].

      Obesity is an increasing problem globally: populations in poor countries as well as affluent ones are at risk [6]. Reports of obesity among pregnant women in the USA range from 18.5% to 38.3%, making it one of the most frequent high-risk obstetric situations [7]. A recent Australian study reported that 34% of pregnant women were overweight or obese; overweight/obese women had increased adverse maternal and neonatal outcomes, resulting in increased costs of obstetric care [8]. The increase in maternal obesity is accelerating, and is associated with socio-economic disadvantage [9]. It has been recognised that obesity may track across generations, thus prevention is an urgent priority [10].

      In 1992, Rutishauser & Carlin reported a negative relationship between maternal obesity and breastfeeding duration and they stated that this was the first study to investigate the effect of over- rather than under-nutrition on the duration of breastfeeding [11]. Since then, a number of studies have found lower rates of breastfeeding in women who are overweight and obese compared to women of normal weight [1214]. Some researchers have attributed this to physiological causes, such as delayed lactogenesis ("milk coming in") [15] and lower prolactin response [16]. However, as obese women are more likely to belong to subgroups of women with lower rates of breastfeeding than normal weight women, such as lower socioeconomic status [17] and higher depression [18], it is necessary to adjust for these potential confounding factors.

      This is an important public health issue as the increasing incidence of maternal obesity and the apparent association with increased artificial feeding of infants will lead to an increasing risk of obesity in children. The aim of this paper is to examine the relationship between maternal overweight and obesity and breastfeeding intention and initiation and duration.

      Methods

      A systematic review was conducted in January and February 2007 using the key words "(obesity OR BMI) AND (breastf* OR lactation OR lactating)". The following databases were searched (all languages, from the start of the database):

      • Medline via PubMed (8 February 2007) 767 items, 24 were relevant;

      • CINAHL (Cumulative Index to Nursing & Allied Health Literature) (8 February 2007) 103 items, 11 relevant (1 additional);

      • Australian Breastfeeding Association's Lactation Resource Centre database was searched for 'obesity' (21 January 2007); 172 items, 10 relevant (3 additional).

      Most of the articles found in the databases were about the relationship between breastfeeding and childhood obesity and were therefore not relevant to this review. All papers related to maternal overweight and obesity and infant feeding were located and included if appropriate. Papers that were case studies, clinical papers or reviews were not included in the tables [1928]. Research studies were also identified from the reference lists of included articles, and the authors' literature collection was hand-searched (n = 2230; nine additional studies). Papers which had cited the original Rutishauser and Carlin study were identified (n = 6), but no new papers were revealed. The total number of research articles included in this review is 27.

      Five papers were excluded as they did not define overweight or obesity (e.g. presented body mass index (BMI, kg/m2) as a continuous variable [2932] or used vague terms, such as "heavy before becoming pregnant" [33]). However, as there were very few studies on women's infant feeding intention and maternal overweight and obesity, a study which examined women's "weight concerns" was included [34] as this information was also relevant. Thus, 22 papers are included in the tables (27 less 5).

      Most studies based their evaluation of maternal obesity on the World Health Organization (WHO) definition of obesity [35]: normal weight BMI<25, overweight BMI 25 ≤ 30, obese BMI > 30, or the US Institute of Medicine (IOM) definition [36]: underweight/normal weight BMI < 26.1, overweight BMI 26.1 – 29.0, obese BMI > 29.0.

      The papers have been grouped according to the content of the study and presented in tables alphabetically by the first author. As women's infant feeding intention has been found to be the strongest single predictor of breastfeeding behaviour [37], all studies reporting infant feeding intention and maternal obesity, including those with "vague" definitions, have been included in Table 1 (Included studies on maternal obesity and women's infant feeding intentions).
      Table 1

      Included studies on maternal obesity and women's infant feeding intentions

      Authors, Year of Publication, Country, and Year(s) of Study

      Participants

      Definitions

      Results

      Barnes et al, 1997 [34], Bristol, UK, 1991-112

      Birth cohort, (Avon Longitudinal Study of Parents and Children) n = 11,907

      Multivariate analysis, n = 8431 for 1st week and n = 8392 for 4 months

      Intention: asked at 32 weeks (4 time periods, 4 options for each)

      Eating Disorder Examination Questionnaire, including 'shape concern' and 'weight concern' items (> 2 indicated marked concern)

      Intention to bf 1 week old infant:

      Shape concern normal OR 1.22 (95%CI: 1.10, 1.35)

      Weight concern normal OR 1.20 (95%CI, 1.07, 1.35)

      Intention to bf infant up to 4 months:

      Shape concern normal OR 1.30 (95%CI: 1.19, 1.42)

      Weight concern normal OR 1.26 (95%CI: 1.14, 1.40)

      Multivariate analysis:

      Intention to bf 1 week old infant:

      Shape concern normal OR 1.25 (95%CI: 1.09, 1.42)

      Weight concern normal NS

      Intention to bf infant up to 4 months:

      Shape concern normal OR 1.26 (95%CI: 1.13, 1.42)

      Weight concern normal OR 1.16 (95%CI: 1.02, 1.32)

      (Adjusted for demographic variables, smoking, maternal attitudes to baby)

      Foster et al 1996 [41], Manchester, UK, yr of study not stated

      Antenatal cohort n = 38

      Eating Disorder Examination: Shape Concern (SC).

      Body Satisfaction Scale:

      General Satisfaction (GS).

      Measurement of BMI not mentioned in text

      Bf intention and BMI: NS

      Shape concern:

      Intended to bf median 0.29

      Intended to formula feed median 1.05 (i.e. higher concern)

      (p = 0.02)

      General Satisfaction:

      Intended to bf median 38.5

      Intended to formula feed median 47.5 (i.e. higher dissatisfaction)

      (p = 0.004)

      Multivariate analysis: body shape satisfaction independent predictor of infant feeding intention.

      (Adjusted for social class, GS, SC and maternal-fetal attachment)

      Hilson et al 2004 [42], Cooperstown, NY, USA, 1998

      Antenatal cohort Eligibility: intended to bf, singleton infant n = 114

      IOM definition of obesity Self-reported height and weight

      Planned intention (months, mean, sd)

      Underweight/normal weight 9.3 (5.7)

      Overweight 9.8 (3.0)

      Obese 6.9 (4.6)

      (p < 0.05)

      Bf = breastfeeding, BMI = body mass index, IOM = Institute of Medicine, NS = not significant

      The indicators suggested for monitoring breastfeeding have been described as:

      • Initiation (the infant's first intake of breast milk)

      • Intensity (the degree of exclusiveness of breast milk as the source of nourishment for the infant) and

      • Total duration (the total length of time that an infant receives any breast milk at all [38].

      Authorities recommend that breastfeeding initiation is defined as "ever breastfed/ever given breast milk" so that infants who only went to the breast once or only received expressed breast milk are included [38]. However, research studies have used a range of definitions, including breastfeeding at hospital discharge [12], breastfeeding at four days [39], feeding in last five feeds in hospital [40]. Table 2 (Included studies on maternal obesity and initiation of breastfeeding) includes the studies which have reported breastfeeding initiation (however defined), and the authors' definition when it varies from "ever breastfed". Where the authors have not presented an odds ratio (OR) for breastfeeding initiation we have calculated one using data from their publication (labelled as "our calculation of overweight/obese women not initiating breastfeeding"). These are unadjusted odds ratios as we did not have the data to adjust for potential confounding factors such as income or method of birth. We have not performed a meta-analysis as the definitions of initiation are inconsistent.
      Table 2

      Included studies on maternal obesity and initiation of breastfeeding

      Authors, Year of Publication, Country, and Year(s) of Study

      Participants

      Definition of obesity

      Results

      Donath & Amir 2000 [13], Australia, 1992–95

      1995 National Health Survey

      Children up to years 4 old n = 2612

      BMI calculated from self-reported height and weight at time of interview

      WHO definition of obesity

      % (95% CI)

      Underweight 89.0 (85.8, 92.2)

      Normal weight 89.2 (87.4, 91.0)

      Overweight 86.9 (84.0, 89.9)

      Obese 82.3 (77.6, 87.0)

      OR* overweight 1.25

      OR* obese 1.78

      Grjibovski et al 2005 [43], Severodvinsk, Russia, 1999

      Antenatal community-based cohort n = 1078

      Pre-pregnancy weight defined as under- normal and over-weight based on "doctor's diagnosis" [82]

      Underweight 98.3%

      Normal 98.7%

      Overweight 100.0%

      NS

      Hilson et al 1997 [12]

      Cooperstown, NY, USA, 1992–94

      Medical record review Eligibility: intended to bf (= bf at birth), healthy singleton infant n = 1109

      IOM definition of obesity

      BMI calculated from pre-pregnancy weight and height

      Quit bf by hospital discharge 2 d after birth:

      Normal 4.3%

      Overweight 8.9%

      Obese 12.2%

      OR* overweight 2.17

      OR* obese 3.09

      Not bf at discharge (of women who attempted bf at birth): Odds Ratio

      Overweight 2.54 (p < 0.05)

      Obese 3.65 (p = 0.0007)

      Hilson et al 2006 [39] Cooperstown, NY, USA, 1988–97

      Expanded previous review of medical records [12]

      Eligibility: intended to bf (= bf at birth), singleton infant, no contraindications to bf, no diabetes n = 2783

      IOM definition of obesity

      BMI calculated from pre-pregnancy weight and height

      Breastfeeding at 4 days:

      Underweight 89.0%

      Normal 90.1%

      Overweight 88.4%

      Obese 82.58%

      Obese women different from underweight and normal

      weight women

      OR* overweight 1.19

      OR* obese 1.92

      Kugyelka et al 2004 [40] upstate New York, 1999–2000

      Medical record review, including paediatric record to 6 months of age, all women of 'Hispanic ethnicity' (n = 235) or 'Black race' (n = 263) Eligibility: healthy mothers (BMI > 19) with healthy single, term infant, who attempted to breastfed

      IOM definition

      BMI calculated from pre-pregnancy weight and height

      Baby put to breast < 2 h:

      Hispanic women: Black women

      Normal 71.8% 75.1%

      Overweight 66.7% 69.2%

      Obese 61.5% 63.8%

      (p < 0.05) (p < 0.05)

      Fed formula only during last 5 feeds in hospital:

      Hispanic women: Black women:

      Normal weight 9.6% 5.1%

      Overweight 12.2% 8.0%

      Obese 12.4% 6.9%

      Hispanic women

      OR* overweight 1.48

      OR* obese 1.50

      Black women

      OR* overweight 1.62

      OR* obese 1.38

      Multivariate analysis:

      Hispanic women: obese OR 1.92 (95% CI 1.20, 3.08) of formula and breast in last 5 feeds before discharge compared to breast only

      (adjusted for maternal age, education, parity, gestation, birth wt, smoking and birth)

      Other groups

      NS

      Li et al 2002 [83] USA, 1988–1994

      The Third National Health and Nutrition Survey (NHANES III), children aged 2 mo to 6 yrs n = 8765 94% response for these children; 99% data of bf available

      BMI calculated from self-reported ht and wt at time of interview.

      WHO definition of obesity

      Ever breastfed:

      Normal 58.1%

      Overweight 46.4%

      Obese 44.8%

      OR* overweight 1.60

      OR* obese 1.71

      Li et al 2003 [49] USA, 1996–98

      Pediatric Nutrition Surveillance System and the Pregnancy Nutrition Surveillance System, children aged < 5 years n = 51,329

      BMI calculated from self-reported pre-pregnancy wt IOM definition of obesity

      Obese women more likely to never breastfeed (p < 0.01)

      OR 1.28 estimated from Figure 1

      Oddy et al 2006 [44] Australia, 1989–1991

      Western Australian Pregnancy Cohort Study.

      Pregnant women recruited from King Edward Memorial Hospital, Perth, WA n = 1803

      BMI calculated from pre-pregnancy weight and height (measured by research midwives)

      WHO definition of obesity

      Never breastfed:

      Normal weight 8.2%

      Overweight 11.4%

      Obese women 12.4%

      NS

      OR* overweight 1.33

      OR* obese 1.47

      Scott et al 2006 [45] Australia, 2002–2003

      2nd Perth Infant Feeding Study, cohort of women recruited in hospital. n = 587

      Measurement of maternal weight and height not reported

      WHO definition of obesity

      Any breastfeeding at hospital discharge:

      Normal weight 95.6%

      Overweight 91.5%

      Obese 90.7%

      OR 0.45 (95% CI 0.19, 1.09)

      OR* overweight 2.02

      OR* obese 2.23

      Exclusive breastfeeding at hospital discharge:

      Multivariate analysis, Adjusted OR (95% CI):

      Normal weight 1 (ref)

      Overweight 0.50 (0.28, 0.89)

      Obese 0.63 (0.33, 1.20)

      (adjusted for maternal age, smoking, marital status, occupation, country of birth, parity, antenatal classes, timing of infant feeding decision, delivery, birth weight, special care nursery, mothers' infant feeding attitude, fathers' infant feeding preference, grandmothers' infant feeding preference, whether grandmother had bf)

      OR* overweight 2.00

      OR* obese 1.59

      Sebire et al 2001 [14] UK, 1989–1997

      St Mary's Maternity Information system database, North West Thames region n = 325,395

      BMI calculated from weight at antenatal booking

      Normal BMI 20-<25

      Moderately obese 25-<30

      Very obese BMI > 30

      (BMI < 20 = underweight - excluded from study)

      Bf at hospital discharge:

      Multivariate analysis, Adjusted OR (99% CI):

      Normal weight 1 (ref)

      Mod obese 0.86 (0.84, 0.88)

      Very obese 0.58 (0.56, 0.60)

      (adjusted for ethnic group, parity, age, history of hypertension, diabetes)

      OR* overweight 1.16

      OR* obese 1.72

      bf = breastfed, BMI = body mass index, ht = height, IOM = Institute of Medicine, mo = month, NS = not significant, OR* = our calculation of overweight and obese women not initiating bf compared with normal weight women, WHO = World Health Organization, wk = week, wt = weight

      It has been hypothesised that the onset of lactation occurs later in obese women than other women, therefore all studies which have investigated this are listed in Table 3 (Included studies on maternal obesity and delayed onset of lactation).
      Table 3

      Included studies on maternal obesity and delayed onset of lactation

      Authors, Year of Publication, Country, and Year(s) of Study

      Participants

      Definition of obesity

      Results

      Chapman & Perez-Escamilla 1999 [15] USA 1996–1997

      Hartford Hospital, Connecticut Healthy, single, term infant n = 192

      Women's bodies were classified as slim, average, heavy or obese

      Delayed lactogenesis (> 72 hours)

      Slim/average build 26.4%

      Heavy/obese build 52.2%

      Multivariate analysis

      Heavy/obese build OR 3.2 (95 CI% 1.5, 6.7)

      (adjusted for birth weight, method of birth, ethnicity, serious medical condition, parity, formula feeding day 2)

      Chapman & Perez-Escamilla 2000 [46] USA 1997–1998

      Connecticut Healthy mothers with a healthy, single, term infant n = 57

      Definition of obesity: at least 2 of 3:

      1. BMI at 72 h > 30,

      2. subscapular skin fold thickness at 72 h > 33.7 mm (> 85%ile)

      3. heavy/obese build on day 1.

      Multivariate analysis

      Onset -Milk transfer at 60 h (< or > 9.2 g/feed)

      Obese: OR 6.14 (95%CI: 1.10, 37.41, p = 0.05) compared to non-obese

      Onset – Maternal perception (< or > 72 h)

      Obese: OR 1.97 (95%CI: 0.29, 13.41, p = 0.49) compared to non-obese

      Non-obese:

      Women who bf more frequently had higher milk transfer values and earlier onset of lactogenesis, than women who bf less frequently

      Obese:

      No relationship between these variables

      Dewey et al 2003 [47] USA 1999

      Davis, California Healthy, single, term infants, planning to bf > 1 m n = 280

      BMI measured 2 weeks postpartum BMI > 27.0 taken as overweight/obese

      Delayed lactogenesis (> 72 hours)

      Normal 16%

      Overweight/obese 33%

      p < 0.05

      Multivariate analysis for delayed lactogenesis:

      Overweight/obese: RR 2.46 (95%CI: 1.45, 3.64)

      (adjusted for C-section, parity, flat nipples, birth weight):

      Multivariate analysis for suboptimal infant feeding behaviour on day 7:

      Overweight/obese: RR 2.58 (95%CI: 1.07, 5.22).

      Hilson et al 2004 [42] USA 1998

      Bassett Hospital, Cooperstown, NY Intended to bf, singleton infant n = 114

      BMI calculated from pre-pregnancy weight and height

      IOM definition of obesity

      Delayed lactogenesis (> 72 hours)

      Normal 18.5%

      Overweight 30.8%

      Obese 33.3%

      Univariate analysis NS

      Multivariate analysis NS {not enough power to show a difference}

      Rasmussen et al 2004 [16] USA Years of study not stated

      Bassett Healthcare, Cooperstown, NY n = 40

      Pre-pregnancy BMI from medical records

      IOM definition of obesity

      Duration of feed at 7 days postpartum:

      Overweight/obese women: infants fed for longer: 23.2 (sd 5.6) mins, compared to 15.3 (sd 6.1) mins for normal weight women (p < 0.005)

      Prolactin response to suckling (ng/ml):

      48 hours

      Normal women 26.0 (sd 61.5)

      Overweight/obese women -10.3 (sd 28.3)

      p < 0.05

      Prolactin response to suckling (ng/ml):

      7 days

      Normal women 80.9 (sd 67.6)

      Overweight/obese women 57.1 (sd 60.2)

      NS

      Other hormones (insulin, estradiol, progesterone): NS difference between groups. However, insulin levels were 44% higher in overweight/obese women at 7 days (non-fasting levels and inadequate power).

      Path analysis: effect of pre-pregnant BMI on prolactin response at 7 days: -30.9 ng/ml.

      The final table (Table 4. Included studies on maternal obesity and duration of breastfeeding) includes studies which report total duration of breastfeeding and, where reported, exclusive breastfeeding; multivariate analysis has been included when this has been conducted.
      Table 4

      Included studies on maternal obesity and duration of breastfeeding

      Authors, Year of Publication, Country, and Year(s) of Study

      Participants

      Definition of obesity

      Results

      Amine et al 1989 [51] Kuwait, Year of study not given

      Multistage, stratified sample, mothers of children < 3 years old n = 2833

      Height and weight recorded at interview Results expressed as % of reference standard weight for height (Nutrition Institute in Cairo, Egypt)

      Mean duration of breastfeeding (month):

      Weight as % reference median:

      80% 4.48 (sd 2.3)

      85–119% 5.46 (sd 3.1)

      120% 6.36 (sd 3.6)

      Baker 2004 [50] Denmark, 1996 onwards

      National Birth Cohort Excluded infants <2500 g, <37w gestation, illnesses or conditions expected to negatively affect growth, mother <18y, never breastfeed, mother diabetic n = 3768

      BMI calculated from pre-pregnant weight and height

      WHO definition of obesity

      Full breastfeeding

      Underweight 15.5 wk

      Normal weight 16.3 wk

      Overweight 15.6 wk

      Obese 14.9 wk

      Any breastfeeding

      Underweight 29.5 wk

      Normal weight 31.3 wk

      Overweight 29.2 wk

      Obese 27.3 wk

      NS

      Chapman & Perez-Escamilla 2000 [46] USA, 1997–1998

      Connecticut Healthy mothers with a healthy, single, term infant, Caesarean section n = 57

      Definition of obesity: at least 2 of 3:

      1. BMI at 72 h > 30,

      2. subscapular skin fold thickness at 72 h > 33.7 mm (> 85%ile)

      3. heavy/obese build on day 1

      Multivariate analysis, likelihood of not bf:

      Non-obese: OR 2.28 (95%CI: 1.02, 5.11) compared with obese women

      (adjusted for maternal intention, milk transfer and other variables, Table 3, model 1)

      {Sample too small for multivariate analysis}

      Donath & Amir 2000 [13] Australia, 1992–1995

      National Health Survey, 1995 Children up to 4 years old Multivariate analysis: n = 1991

      BMI calculated at time of interview

      WHO definition of obesity

      Mean duration % (95% CI)

      Normal 28.7 (27.7, 29.8)

      Overweight 26.1 (24.3, 28.0)

      Obese 22.7 (20.1, 25.2)

      Multivariate analysis

      Normal 1

      Overweight 1.15 (1.01, 1.31)

      Obese 1.36 (1.15, 1.61)

      p < 0.05

      (adjusted for maternal education, marital status, low income, home ownership)

      Forster et al 2006 [48] Australia, 1999–2001

      Cohort of public patients, Melbourne n = 764

      BMI calculated from self-reported height and weight

      WHO definition of obesity

      Any breastfeeding at 6 months:

      Underweight 60.0%

      Normal 57.0%

      Overweight 51.9%

      Obese 37.2%

      Multivariate analysis: OR (95% CI)

      Underweight 1.15 (0.70, 1.88)

      Normal 1

      Overweight 0.70 (0.43, 1.12)

      Obese 0.49 (0.28, 0.85)

      (adjusted for intention, breastfed as a baby, maternal age, smoking, region of birth, attended childbirth education, had formula in hospital, maternal anxiety/depression)

      Grjibovski et al 2005 [43] Russia, 1999

      Community-based cohort, all pregnant women at antenatal clinics, Severodvinsk n = 1078

      Pre-pregnancy weight

      Defined as under-, normal and over-weight based on "doctor's diagnosis" [82]

      Median duration (months, 25th, 75 th percentile):

      Underweight 5.50 (3.00, 12.00)

      Normal 5.00 (3.00, 9.00)

      Overweight 4.25 (2.00, 8.00)

      NS

      Multivariate analysis NS

      Hilson et al 1997 [12] USA, 1992–1994

      Medical record review. Bassett Hospital, Cooperstown, NY Healthy singleton infant n = 1109

      BMI calculated from pre-pregnancy weight and height

      IOM definition of obesity

      Exclusive breastfeeding:

      Proportional hazards regression:

      Overweight RR 1.42, p < 0.04

      Obese 1.43, p < 0.02

      Any breastfeeding:

      Proportional hazards regression:

      Overweight RR 1.68, p < 0.006

      Obese 1.73, p < 0.001

      (adjusted for maternal age, smoking, education, gestation, WIC, parity, birth weight, C. section, diabetes)

      Hilson et al 2004 [42] USA, 1998

      Bassett Hospital, Cooperstown, NY

      Intended to bf, singleton infant. n = 114

      BMI calculated from pre-pregnancy weight and height

      IOM definition of obesity

      Exclusive breastfeeding (wks, mean, sd)

      Underweight/normal 3.6 (3.9)

      Overweight 2.6 (3.2)

      Obese 2.7 (2.3)

      Any breastfeeding (wks, mean, sd)

      Underweight/normal 7.3 (8.9)

      Overweight 5.6 (5.4)

      Obese 4.6 (4.6)

      RR discontinuing bf: obese 2.43 (95%CI: 1.40, 4.20, p = 0.002) cf to underweight/normal wt women

      Exclusive bf: NS

      Multivariate analysis: RR = 2.03 (95%CI: 1.07, 4.5, p = 0.03)

      (adjusted for infant feeding intention, work/school, satisfaction with appearance, indifference to bf)

      Hilson et al 2006 [39] USA, 1988–1997

      Expanded previous review of medical records [12].

      Bassett Hospital, Cooperstown, NY

      Intended to bf, singleton infant.

      No contraindications to bf, no diabetes.

      n = 2783

      BMI calculated from pre-pregnancy weight and height

      IOM definition of obesity

      EBF = last time mother feed only breast milk, without adding non human milk, juice, solids

      ABF = last feeding of any breast milk to infant

      Median duration of EBF (wks):

      Underweight 1.7

      Normal 2.0

      Overweight 1.7

      Obese 1.1

      p < 0.05

      Median duration of ABF (wks):

      Underweight 8.0

      Normal 8.0

      Overweight 7.0

      Obese 2.0

      p < 0.05

      Multivariate analysis: HR of stopping bf:

      Obese 1.50 (95%CI 1.11, 2.03) for normal wt gain in pregnancy

      (adjusted for education, smoking, maternal age, parity, WIC, birth)

      Kugyelka et al 2004 [40] USA, Hispanic women: 1998–2000; Black women: 1999–2000

      Medical record review, upstate New York, all women of 'Hispanic ethnicity' (mainly Puerto Rican) (n = 235) or 'Black race' (n = 263) Healthy mothers who attempted to breastfeed with healthy single, term infant

      BMI calculated from pre-pregnancy height and weight recorded on New York State prenatal form (could be measured or self-reported)

      IOM definition of obesity

      EBF = last time mother feed only breast milk, without adding non human milk ABF = last feeding of any breast milk to infant

      Hispanic women:

      Obesity assoc with shorter duration of EBF (RR: 1.5; 95%CI: 1.1, 2.0) and ABF (RR: 1.6; 95%CI: 1.1, 2.1) compared to normal wt women

      Black women:

      No effect of BMI on duration of EBF or ABF

      Li et al 2002 [83] USA 1988–1994 (exclusive bf: Phase II, 1991–1994)

      The Third National Health and Nutrition Survey (NHANES III) n = 7712

      BMI calculated from self-reported ht and wt at time of interview

      WHO definition of obesity

      Exclusive breastfeeding at 2 months:

      Normal 35.4%

      Overweight 28.2%

      Obese 25.9%

      Breastfeeding at 6 months:

      Normal 25.0%

      Overweight 17.3%

      Obese 16.9%

      Breastfeeding at 12 months:

      Normal 10.0%

      Overweight 5.7%

      Obese 5.6%

      Li et al 2003 [49] USA 1996–1998

      Pediatric Nutrition Surveillance System and the Pregnancy Nutrition Surveillance System Children aged < 5 years n = 124,151 (n for multivariate analysis of women who initiated breastfeeding = 13,234)

      BMI calculated from self-reported pre-pregnancy weight

      IOM definition of obesity

      Adjusted breastfeeding duration (weeks):

      Underweight 13.3

      Normal weight 13.6

      Overweight 13.1

      Obese 11.8

      (p < 0.01)

      (adjusted for gestational weight gain, birth weight, gestation, parity, maternal age, education, marital status, race, smoking, prenatal care, poverty-income ratio)

      Oddy et al 2006 [44] Australia 1989–1991

      Western Australian Pregnancy Cohort Study. Antenatal cohort, King Edward Memorial Hospital, Perth, WA n = 1803

      BMI calculated from pre-pregnancy weight and height (measured by research midwives) WHO definition of obesity

      Breastfeeding < 2 months:

      Normal weight 24.0%

      Overweight 33.6%

      Obese women 41.6%

      p < 0.0005

      Breastfeeding < 4 months:

      Normal weight 37.9%

      Overweight 50.2%

      Obese women 57.5%

      p < 0.0005

      Breastfeeding < 6 months:

      Normal weight 49.0%

      Overweight 59.7%

      Obese women 62.8%

      p = 0.001

      Multivariate Cox hazards regression model:

      HR (adj) = 1.18 (95%CI 1.05, 1.34) for breastfeeding per month (adjusted for education, maternal age, pregnancy problems, older siblings, smoking, solids before 4 months).

      Rutishauser & Carlin 1992 [11] Australia 1984–1985

      Primiparas breastfeeding > 14 days Barwon region, Victoria n = 739

      (N for multivariate analysis between 570 and 600)

      BMI calculated from maternal ht and wt recorded at 1 month postpartum Normal = BMI < 26, Above normal = BMI > 26

      Duration of breastfeeding associated with BMI (p < 0.05)

      Multivariate analysis (Cox proportional hazards):

      HR 1.50 (95%CI 1.11, 2.04)

      (adjusted for smoking, maternal age, time to first breastfeed)

      Scott et al 2006 [84] Australia 2002–2003

      2nd Perth Infant Feeding Study, cohort of women recruited in hospital. n = 587

      Measurement of maternal weight and height not reported

      WHO definition of obesity

      Any breastfeeding at 6 months (other time periods also given):

      Normal 49.0, sd 5.2

      Overweight 48.3, sd 9.5

      Obese: 35.7, sd 10.1

      p < 0.05

      Multivariate analysis NS

      bf = breastfed, BMI = body mass index, ht = height, IOM = Institute of Medicine, mo = month, NS = not significant, WHO = World Health Organization, wk = week, wt = weight

      Results

      There were three studies that examined pregnant women's body mass index [41, 42] or "weight concerns" [34] and their infant feeding intentions (Table 1. Included studies on maternal obesity and women's infant feeding intentions). In a large population-based study in the UK, women identified as having "marked concern" about body shape and weight on a questionnaire were significantly less likely to intend to breastfeed their infant up to four months after adjusting for a range of variables [34]. A small US study found that obese women planned to breastfeed for a shorter duration (6.9 months) than other women (9.3 to 9.8 months) [42].

      Nine of the ten studies of breastfeeding initiation found that overweight and obese women were less likely to commence breastfeeding (Table 2. Included studies on maternal obesity and initiation of breastfeeding). The exception was one study in Russia where virtually all women initiated breastfeeding [43]; the other studies were conducted in the USA (n = 5), Australia (n = 3) and the UK (n = 1). The difference was statistically significant in most studies, but not for black women in the US in the study by Kugyelka [40], nor for women in two studies in Western Australia [44, 45]. The estimated size of the effect (OR of not commencing compared with normal weight women) ranged from 1.19 to 2.17 for overweight women and from 1.38 to 3.09 for obese women in these studies (see Table 2).

      Table 3 shows the five studies which have examined the relationship between obesity and a delayed onset of lactogenesis (the arrival of a copious milk supply). All studies were conducted in the USA and the sample size ranged from 40 to 280. Delayed onset was found in three studies [15, 46, 47]. Overweight/obese women were more likely to have late arrival of milk (33%) than normal women (16%), with a relative risk of 2.46 on multivariate analysis [47]. Infants of overweight/obese women were more likely to have suboptimal feeding behaviour on multivariate analysis (RR 2.58) [47]. One study found that overweight/obese women fed their infants for longer (23 minutes) than normal weight women (15 minutes) and had a lower prolactin response to suckling at 48 hours, but not 7 days, compared to normal weight women [16]. One study didn't have enough power to detect a difference [42]. No study found a faster onset of lactation or improved infant feeding in overweight or obese women.

      A medical record review in the US found that obese women were less likely to have put the baby to the breast within the first two hours than normal weight women [40].

      The studies reporting on maternal obesity and duration of breastfeeding are presented in Table 4. There were fifteen studies, of which seven were conducted in the USA, five in Australia, and one each in Denmark, Kuwait and Russia. The majority of large studies found that obese women breastfed for a shorter duration than normal weight women, even after adjusting for possible confounding factors [1113, 39, 44, 48, 49]. Studies in Russia [43] and Denmark [50] with high breastfeeding initiation rates found no difference in breastfeeding duration according to maternal obesity. A recent Australian study of 764 women found that obese women were less likely to be breastfeeding at six months than women with a normal BMI [48]. Obese women had an odds of 0.49 (95%CI 0.28, 0.85) for breastfeeding at six months compared to women with a normal BMI, adjusted for a range of factors including infant feeding intention, maternal age, smoking and depression [48]. In the USA, Kugyelka and colleagues found no effect of obesity in duration of breastfeeding in black women (while they did find a relationship in Hispanic women) [40]. Only one study, in Kuwait, found that higher maternal weight (120% of standard reference weight for height) was associated with longer duration of breastfeeding [51].

      Discussion

      Possible reasons why overweight/obese women are less likely to breastfeed

      1. Anatomical/physiological

      Several studies have investigated delayed lactogenesis II (the onset of a copious milk supply) in obese women (Table 3). They reported delayed lactogenesis according to maternal perception and to physiological markers. Obesity remained associated with delayed lactogenesis after adjusting for several possible confounding factors, but infant feeding intention was not included. As obese women intend to breastfeed for shorter durations than other women, perhaps part of the delay in time to first feed [40] and tendency to give up before hospital discharge is behavioural rather than physiological.

      Adipose tissue acts as a reservoir for steroid hormones and is also a site of steroid production and metabolism [52, 53]. One theory for the delay in lactogenesis II is that progesterone stored in adipose tissue leads to higher progesterone levels in obese women than normal-weight women which disrupts the usual sudden drop in progesterone leading to lactogenesis II [54]. However the only study to investigate this found no difference in serum progesterone levels between obese/overweight women and normal weight women [16].

      Although women with large breasts are not necessarily obese, obese women will often have large breasts, and there are indications in the literature that large breasts have been associated with breastfeeding difficulties. Historically it was thought that wet nurses with large breasts were poor milk producers [55]. "Overly large breasts usually betrayed a true poverty of milk, for the heavy fat parts impeded the separation of the milk and its free passage through the narrow conduits to the nipples" [[55], p52]. A study of perceived insufficient milk found that women with a high BMI were more likely to experience an earlier onset of "insufficient milk" (p < 0.05), but this was not significant in multivariate survival analysis [56]. In contrast, Rutishauser and Carlin found that overweight/obese women were less likely to give "poor milk supply" as the reason for early cessation of breastfeeding than women of normal weight (p < 0.05) [11].

      Women with large breasts may have practical/mechanical difficulties with attaching the baby to the breast [57, 58]. It can be awkward to support a large breast while assisting a baby to latch on; sometimes the nipple/areola may not be visible to the mother. Some women with large breasts have broad areolae (rather than conical) with short nipples making it difficult to attach the baby [19]. Lactation consultants have noticed that the weight of a large, heavy breast on the infant's chest can interfere with successful attachment [21].

      2. Medical conditions

      Obese and overweight women are over-represented in gynaecological and reproductive medicine clinics [53]. They are more likely to have medical conditions such as polycystic ovary syndrome (PCOS) and diabetes, and to experience obstetric complications and caesarean birth than women of normal weight [28, 59]. Women with diabetes and those who give birth by Caesarean section may be more likely to experience delayed lactogenesis or low milk supply [6062]. Some women with PCOS have insufficient milk supply, which is thought to be related to the endocrinological changes associated with the syndrome (high levels of androgens, insulin resistance, frequently low progesterone levels) [23].

      Some studies have taken this into account by recruiting only women without medical conditions [30, 39] or using multivariate analysis to adjust for these factors [12]. Studies have found that women with early-onset obesity (eg prior to menarche) are more likely to have ovulatory disturbances than women with later-onset obesity [52]. Animal studies have also found that early-onset obesity may negatively affect adult function. Cows with high rates of growth before puberty have less mammary development (as measured by mammary DNA) [63, 64]. A meta-analysis of eight experimental studies of prepubertal weight gain in Holstein heifers, found that first-lactation production increased as weight gains increased up to 799 g/day, however higher weight gains were associated with lower milk production [65]. In humans, breastfeeding success (or duration) has not been studied in relation to the onset of obesity in the mother (i.e. in childhood before the development of the breasts) or in later life

      3. Socio-cultural

      Women who are obese are more likely to belong to social groups who are less likely to breastfeed, such as lower socio-economic status [66, 67] and less likely to have been breastfed themselves [31, 68]. As with women who smoke, obese women have lower intention to breastfeed [37, 69]. Obese women are less likely to participate in preventative health behaviours such having Pap smears and mammography [70]. This may relate to their health beliefs or to feelings of embarrassment with exposure of body parts; it is likely that overweight/obese women may feel more uncomfortable with the idea of breastfeeding in public. Furthermore, large breasts may make if difficult to breastfeed "discretely" and thus "modesty" may another reason for some women to avoid breastfeeding.

      Yet in some cultures, maternal weight appears to have no relationship with infant feeding. Indigenous women in Canada have high levels of overweight and obesity and high levels of breastfeeding [71].

      4. Psychological

      Obese women tend to have greater body image dissatisfaction compared with non-obese women [72]. Women with increased concern about their body shape or weight are less likely to intend to breastfeed [34].

      Obese women tend to have lower self-esteem [73] and poorer mental health than normal weight women [74]. Obese mothers are more likely to have postpartum depression [18]; depressed mothers are less likely to continue breastfeeding than non-depressed mothers [75]. A small study of obese formula-feeding mothers found that they spent less time interacting with infants over a 24 hour testing period than non-obese mothers [76].

      What to do about it?

      Clinicians need to be aware that obese women are at high risk of not breastfeeding, yet a recent study found clinicians did not manage obese women differently from normal weight women [26]. A new review of maternal obesity in pregnancy acknowledged "the increased risk of lactation failure and delay in establishing lactation postdelivery" [[77] p1137], yet did not mention infant feeding in their management guidelines. Obese women may experience a delay in the onset of lactation but in supportive environments breastfeeding can be successfully established.

      Future physiological and epidemiological studies could focus on obese women with a strong intention to breastfeed and without medical or obstetric complications in order to compare breastfeeding success in these women with similar women with normal BMI. To date, no studies have examined this issue from the women's perspective. We urgently need qualitative studies to help us understand obese women and their infant feeding decisions and behaviour. Any potential interventions aimed at helping overweight and obese women to breastfeed successfully need to be evaluated in randomised controlled trials.

      Conclusion

      Breastfeeding behaviour is multifactorial, and a wide range of socio-cultural and physiological variables impact on a woman's decision and ability to breastfeed successfully. Breastfeeding rates vary from population group to group – the variation is usually due to social rather than biological factors. Our analysis of maternal smoking and breastfeeding found that maternal infant feeding intention was a more powerful predictor of breastfeeding duration than whether the mother smoked or not [78]. Smokers with a strong intention to breastfeed were more likely to continue breastfeeding that non-smokers with a low intention to breastfeed, i.e. the social factors were more important than the possible negative physiological effects of nicotine on breast milk supply [78].

      Evidence suggests that lactational performance is not compromised by low BMI [79]; it is still unclear if obesity per se has a role in reduced lactation in overweight and obese women. There are many psychological, behavioral and cultural reasons that may be responsible for reduced lactation in obese women. It is clear that there is a relationship between obesity and variables associated with lower rates of breastfeeding: lower income, depression, body image concerns. Evidence such as obese women's lower intention [34, 41, 42] and a 10% greater chance of not putting the baby to the breast in the first two hours of life [40] will lead to physiological differences between obese women and normal weight women – but the differences may not be due to obesity per se.

      However a number of epidemiological [1113, 39, 44, 48, 49] and animal studies [80, 81] do suggest that maternal obesity is detrimental to lactation. One possibility is that the impact of obesity on lactation is related to the age of development of obesity, as prepubertal obesity is detrimental to lactation in dairy cows [65]. Further studies into the timing of obesity during women's reproductive lifetime may help to clarify this. In addition, qualitative studies as well as quantitative studies should be undertaken to explore the relationship between maternal obesity and breastfeeding.

      Declarations

      Authors’ Affiliations

      (1)
      Mother & Child Health Research, La Trobe University
      (2)
      Clinical Epidemiology and Biostatistics Unit, Murdoch Childrens Research Institute
      (3)
      Department of Paediatrics, University of Melbourne

      References

      1. Kramer MS, Chalmers B, Hodnett ED, Sevkovskaya Z, Dzikovich I, Shapiro S, et al, PROBIT Study Group (Promotion of Breastfeeding Intervention Trial): Promotion of Breastfeeding Intervention Trial (PROBIT): a randomized trial in the Republic of Belarus. JAMA 2001,285(4):413–420.View ArticlePubMed
      2. Taylor JS, Kacmar JE, Nothnagle M, Lawrence RA: A systematic review of the literature associating breastfeeding with type 2 diabetes and gestational diabetes. J Am Coll Nutr 2005,24(5):320–326.PubMed
      3. Harder T, Bergmann R, Kallischnigg G, Plagemann A: Duration of breastfeeding and risk of overweight: A meta-analysis. Am J Epidemiol 2005, 162:397–403.View ArticlePubMed
      4. Owen CG, Martin RM, Whincup PH, Davey Smith G, Cook DG: Effect of infant feeding on the risk of obesity across the life course: A quantitative review of published evidence. Pediatrics 2005,115(5):1367–1377.View ArticlePubMed
      5. Akobeng AK, Heller RF: Assessing the population impact of low rates of breastfeeding on asthma, coeliac disease and obesity: the use of a new statistical method. Arch Dis Child 2007,92(6):483–485.View ArticlePubMed
      6. World Health Organization: Obesity: preventing and managing the global epidemic: report of a WHO consultation. World Health Organ Tech Rep Ser 2000, 894:i-253.
      7. Galtier-Dereure F, Boegner C, Bringer J: Obesity and pregnancy: complications and cost. Am J Clin Nutr 2000, 71(suppl):1242S-48S.
      8. Callaway LK, Prins JB, Chang AM, McIntyre HD: The prevalence and impact of overweight and obesity in an Australian population. Med J Aust 2006,184(2):56–59.PubMed
      9. Heslehurst N, Ells LJ, Batterham A, Wilkinson J, Summerbell CD: Trends in maternal obesity incidence rates, demographic predictors, and health inequalities in 36 821 women over a 15-year period . BJOG 2007,114(2):187–194.View ArticlePubMed
      10. Johnson DB, Gerstein DE, Evans AE, Woodward-Lopez G: Preventing obesity: A life cycle perspective. J Am Diet Assoc 2006, 106:97–102.View ArticlePubMed
      11. Rutishauser IHE, Carlin JB: Body mass index and duration of breast feeding: a survival analysis during the first six months of life. J Epidemiol Community Health 1992, 46:559–565.View ArticlePubMed
      12. Hilson JA, Rasmussen KM, Kjolhede CL: Maternal obesity and breast-feeding success in a rural population of white women. Am J Clin Nutr 1997, 66:1371–1378.PubMed
      13. Donath SM, Amir LH: Does maternal obesity adversely affect breastfeeding initiation and duration? J Paediatr Child Health 2000, 36:482–486.View ArticlePubMed
      14. Sebire NJ, Jolly M, Harris JP, Wadsworth J, Joffe M, Beard RW, Regan L, Robinson S: Maternal obesity and pregnancy outcome: a study of 287,213 pregnancies in London. Int J Obes Relat Metab Disord 2001,25(8):1175–1182.View ArticlePubMed
      15. Chapman DJ, Perez-Escamilla R: Identification of risk factors for delayed onset of lactation. J Am Diet Assoc 1999, 99:450–454.View ArticlePubMed
      16. Rasmussen KM, Kjolhede CL: Prepregnant overweight and obesity diminish the prolactin response to suckling in the first week postpartum. Pediatrics 2004, 113:e465-e471.View ArticlePubMed
      17. Rennie KL, Jebb SA: Prevalence of obesity in Great Britain. Obesity Reviews 2005, 6:11–12.View ArticlePubMed
      18. LaCoursiere DY, Baksh L, Bloebaum L, Varnier MW: Maternal body mass index and self-reported postpartum depressive symptoms. Matern Child Health J 2006,10(4):385–390.View ArticlePubMed
      19. Coates MM: Assisting the newborn to latch on to the very large breast: HELP! J Hum Lact 1989,5(3):131–132.View ArticlePubMed
      20. Durkin D: Lactation compromised in obese mothers. Central Lines 2004,20(4):8.
      21. Hoover K: Latch-on difficulties: a clinical observation (Letter). J Hum Lact 2000,16(1):6.View Article
      22. Loveday CA: Is maternal obesity a cause of poor lactation performance? Nutrition Reviews 2005,63(10):352–355.View Article
      23. Marasco L, Marmet C, Shell E: Polycystic ovary syndrome: A connection to insufficient milk supply? J Hum Lact 2000,16(2):143–148.View ArticlePubMed
      24. Rasmussen KM, Hilson JA, Kjolhede CL: Obesity may impair lactogenesis II. J Nutr 2001, 131:3009S-3011S.PubMed
      25. Rasmussen KM, Hilson JA, Kjolhede CL: Obesity as a risk factor for failure to initiate and sustain lactation. Adv Exp Med Biol 2002, 503:217–222.PubMed
      26. Rasmussen KM, Lee VE, Ledkovsky TB, Kjolhede CL: A description of lactation counseling practices that are used with obese mothers. J Hum Lact 2006,22(3):322–327.View ArticlePubMed
      27. Seidman DS: BMI and duration of breast feeding (letter). J Epidemiol Community Health 1993,47(6):508.View ArticlePubMed
      28. Yu CKH, Teoh TG, Robinson S: Obesity in pregnancy. BJOG 2006,113(10):1117–1125.View ArticlePubMed
      29. Michaelsen KF, Larsen PS, Thomsen BL, Samuelson G: The Copenhagen cohort study on infant nutrition and growth: duration of breastfeeding and influencing factors. Acta Pædiatr 1994,83(6):565–571.View ArticlePubMed
      30. Perez-Escamilla R, Segura-Millan S, Pollitt E, Dewey KG: Determinants of lactation performance across time in an urban population from Mexico. Soc Sci Med 1993,37(8):1069–1078.View ArticlePubMed
      31. Riva E, Banderali G, Agostoni C, Silano M, Radaelli G, Giovannini M: Factors associated with initiation and duration of breastfeeding in Italy. Acta Paediatr 1999, 88:411–415.View ArticlePubMed
      32. Thorsdottir I, Gunnarsdottir I, Palsson GI: Association of birth weight and breastfeeding with coronary heart disease risk factors at the age of 6 years. Nutr Metab Cardiovasc Dis 2003, 13:267–272.View ArticlePubMed
      33. Ferris AM, McCabe LT, Allen LH, Pelto GH: Biological and sociocultural determinants of successful lactation among women in eastern Connecticut. J Am Diet Assoc 1987,87(3):316 -3121.PubMed
      34. Barnes J, Stein A, Smith T, Pollock JI, ALSPAC Study Team: Extreme attitudes to body shape, social and psychological factors and a reluctance to breast feed. J R Soc Med 1997, 90:551–559.PubMed
      35. World Health Organization Expert Committee: Physical status: the use and interpretation of anthropometry. World Health Organ Tech Rep Ser 1995.,854(1–452):
      36. Institute of Medicine: Nutrition during Pregnancy. Washington DC , National Academy Press 1990.
      37. Donath SM, Amir LH, ALSPAC Study Team: Relationship between prenatal infant feeding intention and initiation and duration of breastfeeding: a cohort study. Acta Paediatr 2003,92(3):352–356.View ArticlePubMed
      38. Webb K, Marks GC, Lund-Adams M, Rutishauser IHG, Abraham B: Towards a National System for Monitoring Breastfeeding in Australia: Recommendations for Population Indicators, Definitions and Next Steps. AusInfo, Canberra , Australian Food and Nutrition Monitoring Unit, University of Queensland 2001.
      39. Hilson JA, Rasmussen KM, Kjolhede CL: Excessive weight gain during pregnancy is associated with earlier termination of breast-feeding among white women. J Nutr 2006, 136:140–146.PubMed
      40. Kugyelka JG, Rasmussen KM, Frongillo EA: Maternal obesity is negatively associated with breastfeeding success among Hispanic but not black women. J Nutr 2004, 134:1746–1753.PubMed
      41. Foster SF, Slade P, Wilson K: Body image, maternal fetal attachment, and breast feeding. J Psychosom Res 1996,41(2):181–184.View ArticlePubMed
      42. Hilson JA, Rasmussen KM, Kjolhede CL: High prepregnant body mass index is associated with poor lactation outcomes among white, rural women independent of psychosocial and demographic correlates. J Hum Lact 2004,20(1):18–29.View ArticlePubMed
      43. Grjibovski AM, Yngve A, Bygren LO, Sjostrom M: Socio-demographic determinants of initiation and duration of breastfeeding in northwest Russia. Acta Paediatr 2005, 94:588–594.View ArticlePubMed
      44. Oddy WH, Li J, Landsborough L, Kendall GE, Henderson S, Downie J: The association of maternal overweight and obesity with breastfeeding duration. J Pediatr 2006, 149:185–191.View ArticlePubMed
      45. Scott JA, Binns CW, Graham KI, Oddy WH: Temporal changes in the determinants of breastfeeding initiation. Birth 2006,33(1):37–45.View ArticlePubMed
      46. Chapman DJ, Perez-Escamilla R: Maternal perception of the onset of lactation is a valid, public health indicator of lactogenesis stage II. J Nutr 2000, 130:2972–2980.PubMed
      47. Dewey KG, Nommsen LA, Heinig MJ, Cohen RJ: Risk factors for suboptimal infant breastfeeding behavior, delayed onset of lactation, and excess neonatal weight loss. Pediatrics 2003,112(3):607–619.View ArticlePubMed
      48. Forster D, McLachlan H, Lumley J: Factors associated with continuing to feed any breast milk at six months postpartum in a group of Australian women. Int Breastfeed J 2006, 1:18.View ArticlePubMed
      49. Li R, Jewell S, Grummer-Strawn L: Maternal obesity and breastfeeding practices. Am J Clin Nutr 2003,77(4):931–936.PubMed
      50. Baker JL, Michaelsen KF, Rasmussen KM, Sorensen TIA: Maternal prepregnant body mass index, duration of breastfeeding, and timing of complementary food introduction are associated with infant weight gain. Am J Clin Nutr 2004,80(6):1579–1588.PubMed
      51. Amine EK, Al-Awadi F, Rabie M: Infant feeding pattern and weaning practices in Kuwait. J R Soc Health 1989,109(5):178–180.View ArticlePubMed
      52. Azziz R: Reproductive endocrinologic alterations in female asymptomatic obesity. Fertil Steril 1989, 52:703–725.PubMed
      53. Norman RJ, Clark AM: Obesity and reproductive disorders: a review. Reprod Fertil Dev 1998, 10:55–63.View ArticlePubMed
      54. Akre J: Infant Feeding: The Physiological Basis. Geneva , World Health Organization 1989, 21–23.
      55. Whitaker ED: Blood and milk: medical and popular beliefs before the First World War. Measuring Mamma's Milk: Fascism and the Medicalization of Maternity in Italy Ann Arbor , The University of Michigan Press 2000, 29–61.
      56. Segura-Millan S, Dewey KG, Perez-Escamilla R: Factors associated with perceived insufficient milk in a low-income urban population in Mexico. J Nutr 1994, 124:202–212.PubMed
      57. Walker M: Influence of the maternal anatomy and physiology on lactation. Breastfeeding Management for the Clinician: Using the Evidence Sudbury, Massachusetts , Jones and Bartlett Publishers 2006, 51–82.
      58. McAllan A: Breastfeeding with large breasts.[http://​www.​breastfeeding.​asn.​au/​bfinfo/​large.​html]
      59. Pasquali R, Gambineri A, Pagotto U: The impact of obesity on reproduction in women with polycystic ovary syndrome. BJOG 2006,113(10):1148–1159.View ArticlePubMed
      60. Arthur PG, Smith M, Hartmann PE: Milk lactose, citrate, and glucose as markers of lactogenesis in normal and diabetic women. J Pediatr Gastroenterol Nutr 1989,9(4):488–496.View ArticlePubMed
      61. Neubauer SH, Ferris AM, Chase CG, Fanelli J, Thompson CA, Lammi-Keefe CJ, Clark RM, Jensen RG, Bendel RB, Green KW: Delayed lactogenesis in women with insulin-dependent diabetes mellitus. Am J Clin Nutr 1993, 58:54–60.PubMed
      62. Rowe-Murray HJ, Fisher JRW: Baby Friendly Hospital practices: Cesarean section is a persistent barrier to early initiation of breastfeeding. Birth 2002,29(2):124–131.View ArticlePubMed
      63. Capuco AV, Smith JJ, Waldo DR, Rexroad CE: Influence of prepubertal dietary regimen on mammary growth of Holstein heifers. J Dairy Sci 1995, 78:2709–2725.View ArticlePubMed
      64. Sejrsen K, Purup S, Vestergaard M, Foldager J: High body weight gain and reduced bovine mammary growth: physiological basis and implications for milk yield potential. Domest Anim Endocrinol 2000, 19:93–104.View ArticlePubMed
      65. Zanton GI, Heinrichs AJ: Meta-analysis to assess effect of prepubertal average daily gain of Holstein heifers on first-lactation production. J Dairy Sci 2005, 88:3860–3867.View ArticlePubMed
      66. Wadden TA, Brownell KD, Foster GD: Obesity: responding to the global epidemic. J Consult Clin Psychol 2002,70(3):510–525.View ArticlePubMed
      67. Donath S, Amir LH: Rates of breastfeeding in Australia by State and socioeconomic status: evidence from the 1995 National Health Survey. J Paediatr Child Health 2000,36(2):164–168.View ArticlePubMed
      68. Jones DA, West RR, Newcombe RG: Maternal characteristics associated with the duration of breast-feeding. Midwifery 1986, 2:141–146.View ArticlePubMed
      69. Amir LH, Donath SM: Does maternal smoking have a negative physiological effect on breastfeeding? The epidemiological evidence. Birth 2002,29(2):112–123.View ArticlePubMed
      70. Wee CC, McCarthy EP, Davis RB, Phillips RS: Screening for cervical and breast cancer: is obesity an unrecognized barrier to preventive care? Ann Intern Med 2000,132(9):697–704.PubMed
      71. Vallianatos H, Brennand EA, Raine K, Stephen Q, Petawabano B, Dannenbaum D, Willows ND: Beliefs and practices of first nation women about weight gain during pregnancy and lactation: Implications for women's health. The Canadian Journal of Nursing Research 2006,38(1):102–119.PubMed
      72. Sarwer DB, Wadden TA, Foster GD: Assessment of body image dissatisfaction in obese women: specificity, severity, and clinical significance. J Consult Clin Psychol 1998,66(4):651–654.View ArticlePubMed
      73. Matz PE, Foster GD, Faith MS, Wadden TA: Correlates of body image dissatisfaction among overweight women seeking weight loss. J Consult Clin Psychol 2002,70(4):1040–1044.View ArticlePubMed
      74. Stunkard AJ, Faith MS, Allison KC: Depression and obesity. Biol Psychiatry 2003,54(3):330–337.View ArticlePubMed
      75. Astbury J, Brown S, Lumley J, Small R: Birth events, birth experiences and social differences in postnatal depression. Aust J Public Health 1994, 18:176–184.View ArticlePubMed
      76. Rising R, Lifshitz F: Relationship between maternal obesity and infant feeding-interactions. Nutr J 2005, 4:17.View ArticlePubMed
      77. Krishnamoorthy U, Schram CM, Hill SR: Maternal obesity in pregnancy: Is it time for meaningful research to inform preventive and management strategies? BJOG 2006,113(10):1134–1140.View ArticlePubMed
      78. Donath SM, Amir LH, ALSPAC Study Team: The relationship between maternal smoking and breastfeeding duration after adjustment for maternal infant feeding intention. Acta Paediatr 2004, 93:1514–1518.View ArticlePubMed
      79. Prentice AM, Goldberg GR, Prentice A: Body mass index and lactation performance. Eur J Clin Nutr 1994, 48:S78-S89.PubMed
      80. Rasmussen KM: Effects of under- and overnutrition on lactation in laboratory rats. J Nutr 1998, 128:390S-93S.PubMed
      81. Flint DJ, Travers MT, Barber MC, Binart N, Kelly PA: Diet-induced obesity impairs mammary development and lactogenesis in murine mammary gland. Am J Physiol Endocrinol Metab 2005, 288:E1179–87.View ArticlePubMed
      82. Grjibovski AM, Bygren LO, Svartbo B, Magnus P: Social variations in fetal growth in a Russian setting: an analysis of medical records. Ann Epidemiol 2003, 13:599–605.View ArticlePubMed
      83. Li R, Ogden C, Ballew C, Gillespie C, Grummer-Strawn L: Prevalence of exclusive breastfeeding among US infants: the Third National Health and Nutrition Examination Survey (Phase II, 1991–1994). Am J Public Health 2002,92(7):1107–1110.View ArticlePubMed
      84. Scott JA, Binns CW, Oddy WH, Graham KI: Predictors of breastfeeding duration: evidence from a cohort study. Pediatrics 2006,117(4):e646–55.View ArticlePubMed
      85. Pre-publication history

        1. The pre-publication history for this paper can be accessed here:http://​www.​biomedcentral.​com/​1471-2393/​7/​9/​prepub

      Copyright

      © Amir and Donath. 2007

      This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://​creativecommons.​org/​licenses/​by/​2.​0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.