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Table 1 Characteristics of studies included in the systematic review

From: Caesarean delivery and subsequent pregnancy interval: a systematic review and meta-analysis

Study, year

Country/ Study design

Study period/ Follow-up

Data source

Total sample

Interval used

Statistical tests used

Indication for Caesarean

Parity

Exclusions

Eijsink, 2008 [32]

Holland / Cohort

1998-2002/ Follow-up to 2005

Single hospital database

547

IPI (scale)

Kaplan-Meier curves

Breech emergency & elective

Primiparous

Multiple deliveries, congenital malformations, uterine anomalies

Collin, 2006 [10]

Sub-Saharan Africa / Cohort

1993-2003/ Minimum follow-up 3 years

Cross-sectional standardised survey data from 22 countries

35,398

IPI ( >1 or <5 years)

Cox regression

No

Multiparous

Women with >1 terminated pregnancy; women currently breastfeeding; abstaining from intercourse or using contraception; women in South Africa (due to high elective Caesarean rates); stillbirths; women outside 14–49 years of age

Smith, 2006 [18]

Scotland / Cohort

1980-1984/ Follow-up to 1999

Population-based database

109,991

IPI (scale)

Logistic regression

Emergency, elective for breech, all other pre-labour Caesarean

Primiparous

Multiple births, preterm births, perinatal deaths, missing values

Murphy, 2002 [7]

UK / Cohort

1991-1992/ Minimum follow-up 3 years

Self-completed questionnaire data

3,994

IPI (>1 or >3 years)

Logistic regression

No

Multiparous

Women with unplanned pregnancies

Zdeb, 1984 [33]

USA/ Cohort

1975/ Follow-up for 5 years

Single hospital database

5,513

IPI (scale)

X2 analysis

No

Primiparous

Stillbirths, high-forceps, mid-forceps, breech, version and extraction deliveries

Tollånes, 2007 [16]

Norway/ Cohort

1969-1996/ Follow-up to 2003

Nationwide Birth Register

596,341

BI (scale)

Logistic regression

Breech, pre-eclampsia, low-risk Caesarean groups

Primiparous

Women dying aged <50, women who changed partners, multiple pregnancies

Tower, 2000 [17]

UK / Cohort

1992-1993/ Follow-up for 5 years

Single hospital database

1,152

BI, IPI (scale)

Not stated

Failure to progress, fetal distress

Primiparous

None stated

Huttly, 1990 [34]

Brazil/ Cohort

1982/ Follow-up for 4 years

Data obtained from interview of mothers

4,683

BI (within 35–52 months)

Not stated

No

Multiparous

Tubal ligation/ sterilisation

Hemminki,1987 [37]

Sweden/ Cohort

1973, 1976/ Follow-up for 5 years

Nationwide Birth Register survey data

12,918

BI (<5 years)

X2 analysis

No

Primiparous

Hysterectomy, non-Swedish women, rare blood groups, multiple pregnancies, malformations, birth weight <2000g, perinatal death

LaSala, 1987 [35]

USA/ Case control

1978/ Follow-up for 3 years

Single hospital logbook

570

BI (>2 years)

X2 analysis

No

Primiparous

Missing hospital records, sterilisation, women using contraception

Hemminki,1985 [36]

USA/ Cohort

1957-1982/ Minimum 1 year follow-up, maximum 25 years

Nationwide Birth Register

812

BI (scale)

Kaplan-Meier curves

No

Primiparous

Women outside 15–44 years of age; women living in Alaska or Hawaii; women with no live births or more than two abortions; multiple births; missing data; perinatal deaths; birth weight <1500g; women who put their child up for adoption

  1. Table legend: IPI Inter-pregnancy interval, BI Birth interval. Data for interval categories: Continuous refers to the median/mean IPI or BI, >1 year refers to trying to conceive for more than 1 year, >3 years refers to trying to conceive for greater than 3 years, <5 years refers to conceiving within 5 years, >2 years refers to being sub-fertile for greater than 2 years.