Women who are pregnant or have been pregnant in the past year have a nearly 40% lower risk of dying from natural causes than their nonpregnant counterparts, according to a retrospective, population-based study in Finland.¹ Compared with nonpregnant women of the same age, pregnant and recently pregnant women aged 25–34 and 35–49 had reduced risks of death from cancer (relative risks, 0.3 for each), and those in the latter age-group had a reduced risk of death from diseases of the circulatory system (0.3). However, pregnant and recently pregnant women aged 15–24 had an increased risk of death from diseases of the circulatory system (2.0), which was due mainly to a sharply increased risk of death from cerebrovascular disease after giving birth (4.1). Of note, the majority of deaths from natural causes that occurred during pregnancy and the next year were not related to pregnancy.

To test the hypothesis of a "healthy pregnant woman effect," which proposes that women have a reduced likelihood of dying from medical conditions while pregnant and in the following year, researchers compared the pregnancy-associated death rate (the rate of deaths during pregnancy and the year after its end) among 15–49-year-old women with the death rate among nonpregnant women of the same age. All deaths of women these ages during a 14-year period (1987–2000) in Finland were ascertained from a national death register; deaths were classified as those from natural causes (medical conditions) and those from violent causes (accidents and injuries). Information on births (both live births and stillbirths), induced abortions and the majority of ectopic pregnancies and spontaneous abortions in the study population was obtained by linking mortality data to three other national databases. Analyses were adjusted for age.

During the study period, 15,823 women aged 15–49 died; 3% were pregnant or had been pregnant in the previous year. The pregnancy-associated death rate (37 per 100,000 pregnancies) was lower than the death rate among nonpregnant women (57 per 100,000 person-years). The difference corresponded to an almost 40% reduction in the risk of dying from any cause during pregnancy and the following year (relative risk, 0.6). Women's risk of death from any cause was also reduced after a birth (0.5), but it was elevated after an induced abortion (1.5) and was essentially unchanged after a spontaneous abortion or ectopic pregnancy.

Overall, 18 deaths per 100,000 pregnancies, or slightly fewer than half of pregnancy-associated deaths, were attributable to natural causes; more than three-fourths of these deaths (14 per 100,000 pregnancies) were not related to pregnancy, either directly or indirectly. Like the overall mortality risk, the risk of death from natural causes was about 40% lower among women who were pregnant or had been pregnant in the past year than among nonpregnant women (relative risk, 0.6). More specifically, compared with their nonpregnant counterparts, pregnant and recently pregnant women had reduced risks of death from cancer (relative risk, 0.4) and diseases of the circulatory system (0.7), but risks varied with age. Women aged 25–34 and 35–49 had reduced risks of pregnancy-associated death due to cancer (0.3 for each) and natural causes overall (0.5 and 0.4), and women in the latter age-group also had a reduced risk of death from diseases of the circulatory system (0.3). However, women aged 15–24 had an increased risk of pregnancy-associated death due to diseases of the circulatory system (2.0), reflecting their elevated risk of death from cerebrovascular disease—primarily intracerebral hemorrhage and hemorrhagic stroke—after giving birth (4.1).

Improved care and monitoring during pregnancy and childbirth and after pregnancy could prevent many pregnancy-associated deaths from natural causes, the researchers contend; furthermore, prevention of pregnancy-associated deaths from injuries should not be neglected. "Because the majority of pregnancy-associated deaths were not related to pregnancy, it is important to focus also on [deaths] other than obstetric deaths," they assert. Despite the sharp increase in the risk of death from cerebrovascular disease among pregnant and recently pregnant 15–24-year-olds, the absolute rate of this outcome is low, and its cause remains uncertain, the researchers note; targeting measures to prevent these pregnancy-associated deaths may therefore be difficult.

—S. London

REFERENCE

1. Gissler M et al., Pregnancy-associated mortality after birth, spontaneous abortion, or induced abortion in Finland, 1987–2000, American Journal of Obstetrics and Gynecology, 2004, 190(2):422–427.