The effect of induced abortion on subsequent pregnancy outcome

OBJECTIVE: To investigate the effect of induced abortion on the outcome of the next pregnancy. DESIGN: Long-term prospective controlled cohort study. SETTING: Joint Royal College of General Practitioners/Royal College of Obstetricians and Gynaecologists study based in general practice in England, Scotland and Wales. SUBJECTS: 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). MAIN OUTCOME MEASURES: Non-viable outcome (spontaneous or missed miscarriage, ectopic pregnancy or stillbirth), birthweight, length of gestation. RESULTS: 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. CONCLUSION: Overall, induced abortion was not associated with any important effect on the three measures of adverse outcome in the subsequent pregnancy.