The effect of induced abortion on subsequent pregnancy outcome

To investigate the effect of induced abortion on the outcome of the next pregnancy.

Long-term prospective controlled cohort study.

Joint Royal College of General Practitioners/Royal College of Obstetricians and Gynaecologists study based in general practice in England, Scotland and Wales.

1311 women whose recruitment pregnancy had ended in induced abortion (the abortion group) and 2131 women whose recruitment pregnancy had a natural conclusion (the non-abortion group).

Non-viable outcome (spontaneous or missed miscarriage, ectopic pregnancy or stillbirth), birthweight, length of gestation.

Induced abortion was not materially associated with any of the three measures of adverse outcome. Compared with the non-abortion group the relative risk of a non-viable outcome in the abortion group was 1.01 (95% CI 0.81 to 1.27). In the abortion group birthweight was an average 23 g lighter (95% CI -76 g to + 30 g) and length of gestation an average 0.9 days shorter (95% CI -2.2 days to + 0.4 days) than in the non-abortion group. Women who had their abortions in NHS premises had an increased risk of a non-viable outcome (RR 2.55, 95% CI 1.31 to 4.94) and had babies with significantly lower mean birthweight (-119 g, 95% CI -233 g to +5 g) compared with those who obtained their operations in the private sector. Women whose abortion had been carried out by a consultant had the lowest risk of non-viable outcome. Although these differences remained after adjustment for a number of important variables, it is possible that factors not measured in the present study, such as economic status and occupation, played a contributory role.

Overall, induced abortion was not associated with any important effect on the three measures of adverse outcome in the subsequent pregnancy.