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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.