The effect of induced abortion on subsequent fertility

Abstract

Objective: To investigate the effect of induced abortion on subsequent fertility.

Design: 1. Prospective cohort study of women who had an unplanned pregnancy at recruitment. 2. Retrospective study of women who had a planned pregnancy at recruitment.

Setting: Joint Royal College of General Practitioners/Royal College of Obstetricians and Gynaecologists study based in general practice in England, Scotland and Wales, between 1976 and 1987.

Subjects: 1. Prospective study: Four hundred and thirty-three women with a recruitment unplanned pregnancy ending in induced abortion (abortion group) and 1035 women with a recruitment unplanned pregnancy which ended naturally (nonabortion group). All subsequently had a planned pregnancy, or were known to be trying to conceive at some point during the follow-up. 2. Retrospective study: Nine thousand two hundred and ninety-nine women who presented at recruitment with a planned pregnancy.

Main outcome measure: The women's estimated length of planning time, expressed as a fertility rate ratio.

Results: Induced abortion was not related to future fertility. In the prospective study, the fertility rate ratio (FRR) of the abortion group relative to the nonabortion group was 0.94 (95% CI 0.83 to 1.07, P = 0.37). This result was supported by the retrospective study, which again showed no important difference between the two groups.

Conclusion: Induced abortion does not appear to have an important effect on future fertility.

PIP: The Joint Royal College of General Practitioners and Royal College of Obstetricians and Gynaecologists sponsored comparative investigation of: 1) a prospective study of women with an unplanned pregnancy (433 women chose induced abortions and 1035 women continued their pregnancies) between 1976 and 1979 who were followed through 1987 and 2) a retrospective study of 9299 women with a planned pregnancy between 1976 and 1979. All the women were recruited at a general practice in England, Scotland, or Wales. The researchers wanted to examine the relationship between induced abortion and future fertility. They used Cox's Proportional Hazards Model for survival analysis in both studies. No significant differences in the fertility curves between the abortion and nonabortion groups existed in the prospective study. The overall fertility rate ratio (FRR) of the abortion group was 0.94. Fewer women in the abortion group who had had just one previous pregnancy conceived than the same gravida women who were in the nonabortion group, and the difference approached significance (e.g., at 12 months, 89% vs. 93.3%; p = .068). The retrospective study did not confirm this finding, however. Women who had undergone one induced abortion before recruitment into the retrospective study experienced essentially the same fertility as those in the nonabortion group (FRR - 1.02). Further, women who had had at least two induced abortions experienced essentially the same fertility as those who had had at least two natural pregnancy outcomes (FRR = 0.93). These results indicated that induced abortion does not significantly affect subsequent fertility.