Increased risk of prematurity in first births after several induced abortions

Several induced abortions before the first birth increase the risk of prematurity. The increased risk is very small, however, and women who have experienced induced abortion should not be alarmed.

According to a register-based study conducted by the National Institute for Health and Welfare around 10 per cent of Finnish first-time mothers have previously had an induced abortion. 1.5 per cent of all first-time mothers have had two induced abortion and 0.3 per cent three or more abortions. The study included just over 300 000 first-time mothers.

Women who have had three or more induced abortions had a higher risk of delivering a baby prematurely or with a low birth weight. Low or very low birth weight indicates a birth weight of less than 2500g and 1500g respectively and preterm or very preterm birth indicates birth before 37 and 28 weeks respectively. There was a slightly increased risk of a very preterm birth for women who had had two induced abortions.

The study also showed a small increased risk of perinatal mortality for first-time mothers whose first pregnancy resulted in an induced abortion. However, this was probably due to differences in the mother's other background factors instead of induced abortions. Concerning health behaviour factors, the study could control only crudely for smoking and social background.

THL's register-based study shows a link between poor birth outcomes and induced abortions. The researchers emphasise, however, that the study could not control for all possible confounding factors and that adverse birth outcomes can be caused by some of these other factors. They suggest, however, that the research results could be used in education and communications about sexual and reproductive health.

Finland has one of the lowest rates of induced abortion in Europe: 8.7 induced abortions per 1000 women aged 15–49. Induced abortion is one of the most common gynaecological procedures performed on women but the impact of induced abortions on women’s subsequent childbearing has not yet been properly studied.

The now published Finnish register-based study is the first large-scale study to look at a broad set of perinatal outcomes. It is adjusted for several confounding factors such as maternal age, marital status, smoking, socioeconomic position and previous pregnancies.

Source:
R. Klemetti , M. Gissler, M. Niinimäki and E. Hemminki: Birth outcomes after induced abortion: a nationwide register-based study of first births in Finland. Human Reproduction, Advance Access, 10.1093/humrep/des294.

More information:

Elina Hemminki
Research Professor
THL
tel. +358 29 524 7307

Reija Klemetti
Senior Researcher
THL
tel. +358 29 524 7265
firstname.lastname@thl.fi