Table 2 Characteristics of included studies
Study Information | Participants | Supplements | Measurement | Quality | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Study | Country | Study design | Study groups | Number | Age | Inclusion criteria | Exclusion criteria | Supplement type and dose | Number with available data | Estimated compliance: N (%) | Data collection method (s) | Time period(s) | Quality rating |
Baker et.al (2009) [23] | UK | Cross-sectional study | NA | 500 | 14–18 | Singleton pregnancy, age 14–18, gestational age < =20 weeks | Inability to provide informed consent, preeclampsia, clotting disorders, HIV/AIDS, haemoglobinopathies, diabetes, renal disease, hypertension, multiple gestations, history of 3= > previous miscarriages | Preconception folic acid | 498 | 34 (6.9) | 24 h recall (multiple) | Third trimester | + |
Folic acid in early pregnancy | 498 | 220 (44.2) | |||||||||||
Iron in early pregnancy | 498 | 39 (7.8) | |||||||||||
Multivitamins in early pregnancy | 498 | 19 (3.8) | |||||||||||
Folic acid only in 3rd trimester | 290 | 5 (1.7) | |||||||||||
Iron and folic acid in 3rd trimester | 290 | 13 (4.5) | |||||||||||
Iron only in 3rd trimester | 290 | 42 (14.5) | |||||||||||
Multivitamins in 3rd trimester | 290 | 7 (2.4) | |||||||||||
Castillo-Duran et.al (2001) [43] | Chile | RCT | Zinc supplemented | 249 | 16.4 (mean) | Beginning prenatal visits before 20 weeks gestation, aged <19 at estimated due date | Adolescents whose background included chronic diseases, drug abuse, mental retardation, illiteracy or pregnancy due to incest or rape | 20 mg Zinc sulphate daily | Intervention group - 249 | At least 50 % compliance | 24 h recall (multiple) | Second and third trimester | + |
Placebo | 258 | 40 mg iron sulphate | All participants - 507 | ||||||||||
Chan et.al (2006) [24] | USA | RCT | Control group, 2 intervention groups excluded from review* | 23 | 15–17 | Enrolled before 20 weeks gestation | Hypertension, diabetes, renal or liver disease, alcohol or tobacco use, using medicines effecting Ca metabolism | No additional supplements reported | Food diary (weighing not mentioned) | Second and third trimester | −/+ | ||
Chang et.al (2003) [37] | USA | Retrospective chart review | NA | 918 | 12–17 | Self-reported racial group as African-American; singleton pregnancy | Birth results not available due to abortion, miscarriage or transfer of care | 90 mg carbonyl iron daily plus additional up to 120 mg for those classified as anaemic | 918 | Not reported | Not reported | Second and third trimester | + |
Dawson et.al (2000) [35] | USA | RCT | One-A-Day without Iron | 20 | 16–20 | Aged 16–20, less than 16 weeks gestation, no iron supplementation for previous 30 days | Hypertension; diabetes; other medical problems; haemoglobin <11 g/dL; haematocrit <30 % | Vitamin A 5000 IU, vitamin D 400 IU, vitamin E 10 mg, vitamin C 60 mg, folic acid 0.4 mg, thiamine 1.5 mg, riboflavin 1.7 mg, niacin 20 mg, pyridoxine 2 mg, vitamin B- 6 mg, pantothenic acid 10 mg | 20 | Not reported | Venous blood sample | Second and third trimester and delivery | −/+ |
One-A-Day with Iron | 20 | 18 mg Iron, Vitamin A 5000 IU, vitamin D 400 IU, vitamin E 10 mg, vitamin C 60 mg, folic acid 0.4 mg, thiamine 1.5 mg, riboflavin 1.7 mg, niacin 20 mg, pyridoxine 2 mg, vitamin B- 6 mg, pantothenic acid 10 mg | 20 | ||||||||||
Derbyshire (2009) [39] | UK | Cross-sectional study | NA | 20 | 15–19 | Attending antenatal classes or community clinics | Incomplete diary | None reported | Food diary unweighed | Third trimester | + | ||
Gadowsky et.al (1995) [42] | Canada | Cross-sectional study | NA | 58 | 14–19 | Not reported | Not reported | Folic Acid Mean 479 μg/day | 58 | 82 % | Venous blood sample | Third trimester | + |
Elemental Iron Mean 31.5 mg/day | |||||||||||||
Cyanocobalamin (B12) Mean 2.24 μg/d | |||||||||||||
Giddens et.al (2000) [27] | USA | RCT (subset from a larger study) | NA | 59 | 13–18 | Singleton pregnancies, between 13 and 19 weeks gestation | Not reported | Reported that any contribution from supplements was not included in analysis | Food diary weighed | Mean over pregnancy | −/+ | ||
Ginde et.al (2010) [32] | USA | Secondary analysis of cross sectional survey | NA | 84 | 13–19 | Not reported | Not reported | Some participants taking vitamin D supplements | Not reported | Not reported | Venous blood sample | Mean over pregnancy | + |
Gutierrez et.al (1999) [28] | USA | Cross-sectional study | NA | 46 | 13–18 | Self-identified ethnicity as Mexican American, primigravida, 13–18 years of age | History of miscarriage or health problems, involved in competitive athletic performances or heavy exercise, planned to move away during study period | None reported | 24 h recall (single) | Second and third trimester | + | ||
Iannotti et.al (2005) [36] | USA | Cross-sectional study | NA | 80 | 13–18 | Self-reported racial group as African-American; singleton pregnancy | Not reported | None reported | 10 ml Venous blood sample | Second and third trimesters | + | ||
Job et.al (1995) [41] | Australia | Cross-sectional study | NA | 35 | 13–19 | Not reported | Not reported | None reported | 24 h recall | Mean over pregnancy | + | ||
Lee et.al (2013) [25] | USA | Cross-sectional study | NA | 156 | 13–18 | Age 18 or under, carrying a single fetus, 12–30 weeks gestation at recruitment | Not reported | Reported that any contribution from supplements was not included in analysis | 24 h recall (multiple) | <23 weeks gestation, 23–30 weeks gestation and Mean over pregnancy | + | ||
McGuire et.al. (2010) [31] | USA | Cross-sectional study | NA | 80 | Under 18 (mean 16.5) | Self-reported ethnic group as African American, singleton pregnancy | Not reported | Routinely prescribed prenatal supplements containing 400 IU vitamin D | Data not available | Venous blood sample | Second and third trimester | + | |
Meier et.al (2002) [34] | USA | RCT | Iron supplemented | 20 | 15–18 | Not reported | Iron deficiency anaemia at recruitment | 60 mg elemental iron & 1 mg folic acid | 20 | Venous blood sample | Second and third trimesters | + | |
Placebo | 17 | 1 mg folic acid | 17 | ||||||||||
Mistry et.al (2014) [40] | UK | Cross-sectional study | Appropriate for gestational age babies | 107 | 14–18 | Not reported | Inability to provide informed consent, pre-eclampsia, clotting disorders, HIV/AIDS, Haemoglobinpathies, diabetes, renal disease, hypertension, multiple pregnancy and previous miscarriage | None reported | 30 ml venous blood sample | Third trimester | + | ||
Small for gestational age babies | 9 | ||||||||||||
O’Brien et.al (2003) [33] | USA | Cross-sectional study | NA | 23 | Mean 16.5 | First, singleton pregnancies; no medical problems; no medications known to influence calcium metabolism; non-smokers; no history of drug or alcohol abuse | Not reported | Prenatal supplement including 5 mmol Ca | 23 | 39 % | Not reported | Third trimester | + |
Pobocik et.al (2003) [38] | Guam (USA Teritory) | Cross-sectional study | NA | 434 | 14–20 | Not reported | Not reported | Reported that any contribution from supplements was not included in analysis | 24 h recall (single) | Mean over pregnancy | −/+ | ||
Rycel et.al (2009) [44] | Poland | Retro-spective cohort | NA | 102 | 15–18 | Not reported | Not reported | none reported | Venous blood sample | Before and after delivery | −/+ | ||
Young et.al (2010) [29] | USA | Cross-sectional study | NA | 92 | 14–18 | Healthy, singleton pregnancy | HIV, diabetes, pre-eclampsia, eating disorders, malabsorption diseases, self-reported drug use | Prenatal supplement including 27 mg iron | 92 | Not reported | Venous blood sample | Second trimester and delivery | + |
Young et.al (2012) [30] | USA | Cross-sectional study | NA | 171 | Under 18 (mean 17.1) | Healthy, singleton pregnancy | HIV, diabetes, pre-eclampsia, eating disorders, malabsorption diseases | 400 IU Vitamin D supplement given to participants found to be deficient | 46 (estimated from reported percentages) | 26.4 % - daily, 35.8 % at least twice per week | 10 ml venous blood sample | Delivery | + |