Invited Commentary: Induced Abortion and the Risk of Preeclampsia in a Subsequent Pregnancy

Although it is well established that a having a pregnancy that ends in a birth protects against subsequent preeclampsia, it is unclear whether a pregnancy ending in miscarriage or induced abortion confers any protection. In this issue of the Journal, Parker et al. (Am J Epidemiol. 2015;182(8):663-669) examine whether, in nulliparous women, a history of induced abortion is associated with a lower risk of preeclampsia in a later pregnancy, focusing on the hypothesis that endometrial injury facilitates later implantation. The authors take advantage of data obtained by linking several Finnish population-based registries that include detailed data on induced abortions, although information on miscarriages was of lower quality. Parker et al. found a modest reduction in risk among women with a history of induced abortion. However, there was little evidence that risk differed between women who had medical abortions and those who had surgical abortions (the latter of which is presumably associated with a higher degree of injury). History of miscarriage was not associated with preeclampsia risk. Although the study by Parker et al. adds to the evidence that suggests that women with a history of induced abortion have a lower risk of preeclampsia, it is difficult to evaluate whether the observed association is due to having had a previous pregnancy (however short) versus none, to confounding, or to an actual effect of induced abortion.