Repeat abortions increase risk of adverse birth outcomes

The more induced abortions a woman has had, the greater the odds her first delivery will be very preterm (< 28 weeks), according to a new study.

Researchers from Finland used a nationwide Finnish registry to identify more than 300,000 first-time mothers of singletons who gave birth between 1996 and 2008. Among them, 10.3% had 1 prior induced abortion, 1.5% had 2, and 0.3% had 3 or more induced abortions.

Published in Human Reproduction, the study showed that, after adjustment for confounding social factors, a dose-response relationship existed between the number of previous abortions and the risk of very preterm birth. Women who had 3 or more previous induced abortions were almost 3 (OR 2.78; 1.48 to 5.24) times as likely to have a very preterm first child as those who had no previous abortions. Odds ratios for women with 2 prior abortions and 1 prior abortion were 1.19 (0.98 to 1.44) and 1.69 (1.14-2.51), respectively (all 95% confidence intervals).

Risks of preterm birth (<37 weeks) and of very low (<1,500 g) and low (<2,500 g) birth weight were statistically significantly increased only in women with 3 or more abortions. Low Apgar scores were not related to the number of previous abortions. The findings suggested a small increase in perinatal death after a previous induced abortion, with the largest increase associated with 3 or more previous abortions, but again, the increases were statistically insignificant.

Most of the abortions were surgical (88%) and performed before 12 weeks’ gestation (91%).

The investigators were careful not to conclude causality, explaining that the observational study, albeit large and well controlled, does not prove cause and effect. But they recommended that women seeking abortions, particularly repeat ones, and physicians be aware of the possible adverse effects on future births.

Read other articles in this issue of Special Delivery.