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

Table 2 Subgroup analyses of the impact of Caesarean section on subsequent sub-fertility (time to next pregnancy or birth)

Study characteristic	Number of studies included	Pooled OR estimate (95% CI)	I²%
*Overall pooled estimate*	n = 5	0.90 [0.86, 0.93]	30%
*Parity*
Primiparous women only	n = 2	0.91 [0.87, 0.96]	0%
Not limited to primiparous women	n = 3	0.81 [0.73, 0.90]	0%
*By publication date*
Pre-2000	n = 1	0.80 [0.68, 0.94]	NA
Post-2000	n = 4	0.90 [0.86, 0.94]	19%
*Length of follow-up*
<10 years	n = 3	0.81 [0.73, 0.90]	0%
>10 years	n = 2	0.91 [0.87, 0.96]	0%
*Indication for mode of delivery*
Specified*	n = 2	0.92 [0.88, 0.97]	88%
Not specified	n = 3	0.81 [0.73, 0.90]	0%
*By cohort size*
<35,000	n = 2	0.79 [0.67, 0.92]	0%
>35,000	n = 3	0.90 [0.87, 0.95]	13%
*By definition of sub-fertility used*
a. Birth Interval (BI)	n = 2	0.89 [0.84, 0.94]	44%
Inter-pregnancy interval (IPI)	n = 3	0.91 [0.85, 0.97]	45%
b. Categorical measure (e.g. > 3 years)	n = 3	0.81 [0.73, 0.90]	0%
Continuous measure (e.g. median IPI)	n = 2	0.91 [0.87, 0.96]	0%

Table Legend: Data refer to the pooled odds ratio (OR) and 95% confidence interval (CI) for each subgroup analysis. I ² is a statistical measure of heterogeneity between 0% and 100%, with higher percentages implying great heterogeneity. *Specified: refers to the indication for mode of delivery and includes in Smith (2006) [18] assisted (instrumental) vaginal delivery, vaginal breech, elective Caesarean for breech, emergency Caesarean and all other prelabour Caesareans. For Tollanes (2007) [16] includes: breech presentation, low risk obstetric group, and a pre-eclampsia group.

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