Table 1.
Characteristics of studies included in the systematic review
| 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 |
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.