Mode of delivery and the probability of subsequent childbearing: a population-based register study

Abstract

Objective: To investigate the relationship between mode of first delivery and probability of subsequent childbearing.

Design: Population-based study.

Setting: Nationwide study in Sweden.

Population: A cohort of 771 690 women who delivered their first singleton infant in Sweden between 1992 and 2010.

Methods: Using Cox's proportional-hazards regression models, risks of subsequent childbearing were compared across four modes of delivery. Hazard ratios (HRs) were calculated, using 95% confidence intervals (95% CIs).

Main outcome measures: Probability of having a second and third child; interpregnancy interval.

Results: Compared with women who had a spontaneous vaginal first delivery, women who delivered by vacuum extraction were less likely to have a second pregnancy (HR 0.96, 95% CI 0.95-0.97), and the probabilities of a second childbirth were substantially lower among women with a previous emergency caesarean section (HR 0.85, 95% CI 0.84-0.86) or an elective caesarean section (HR 0.82, 95% CI 0.80-0.83). There were no clinically important differences in the median time between first and second pregnancy by mode of first delivery. Compared with women younger than 30 years of age, older women were more negatively affected by a vacuum extraction with respect to the probability of having a second child. A primary vacuum extraction decreased the probability of having a third child by 4%, but having two consecutive vacuum extraction deliveries did not further alter the probability.

Conclusions: A first delivery by vacuum extraction does not reduce the probability of subsequent childbearing to the same extent as a first delivery by emergency or elective caesarean section.

Keywords: Elective caesarean section; emergency caesarean section; mode of delivery; subsequent childbearing; vacuum extraction.