The relationship between Caesarean section and subfertility in a population-based sample of 14 541 pregnancies.

BACKGROUND There has been a threefold increase in the rate of Caesarean section over the past 25 years. The long-term consequences of Caesarean section may include subsequent subfertility. METHODS We investigated the relationship between Caesarean section and subfertility within a cohort of 14 541 pregnant women. RESULTS A history of previous Caesarean section was associated with an increased risk of taking >1 year to conceive from the time of planning a pregnancy, adjusted odds ratio (OR) 1.53 [95% confidence interval (CI) 1.09, 2.14]. This association was stronger for women of parity > or =2, adjusted OR 2.97 (95% CI 1.72, 5.10). Nulliparous women with a history of subfertility were at increased risk of delivery by Caesarean section, adjusted OR 1.56 (1.22, 2.00) and OR 2.33 (1.64, 3.30) for durations of >1 and >3 years respectively. CONCLUSIONS These findings suggest a complex relationship between Caesarean section and subfertility where subfertility may both precede and be a consequence of Caesarean section.