Women who had multiple abortions before giving birth to a first child were more likely to have that child very prematurely or to deliver a child with a low birth weight, according to one of the first large-scale studies to look at the issue.
The study, whose results appear in the European journal Human Reproduction, examined more than 300,000 first-born children in Finland between 1996 and 2008. Finland is suited for studies on abortion because it keeps detailed records on both abortion and childbirth.
Researchers from the University of Helsinki found that, similar to previous, smaller studies, having had an abortion prior to giving birth for the first time is associated with a risk of low birth weight or giving birth prematurely. But that risk is very small.
For women who have had three or more abortions, however, the risks appear to be more likely, the study found.
Specifically, the authors found the risk for having a baby born very premature (earlier than 28 weeks) was only statistically significant for women who'd previously had two abortions or more. Women who'd had three or more abortions were a third more likely to deliver a first baby earlier than 37 weeks, 43 percent more likely to have a baby with a low birth weight and twice as likely to have a baby with a very low birth weight.
But the researchers caution that many caveats come along with the study. One is that because it is observational, in that it looked only at medical records, comparing the birth outcomes for women with varying number of abortions.
"No matter how large and well-controlled, it only shows there is a link between abortion and some adverse birth outcomes," said lead author Reija Klemetti, an epidemiologist at the National Institute for Health and Welfare in Helsinki. "It cannot prove that abortions are the cause."
Klemetti and her coauthors suggest that even though they tried to control for women's socioeconomic status, there could be some connection with women's lifestyles, habits and sexual or reproductive health.
Klemetti also said that the risk needs to be put in perspective. "Our results suggest that induced abortions before the first birth, particularly three or more abortions, are associated with a marginally increased risk during the first birth," she said. "However, the increased risk is very small, particularly after only one or even two abortions, and women should not be alarmed by our findings."
Editor's note: Several readers wondered if the study includes all types of abortions, including "spontaneous abortions," also known as miscarriages. It does not. The researchers considered only "induced abortions," or those performed with the intention of terminating a pregnancy.
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