Cause-specific mortality during and after pregnancy and the definition of maternal death

As part of a study to determine whether maternal mortality in Canada is under- reported, we explored the validity of including deaths not directly related to pregnancy. We linked live birth and stillbirth registrations to death registrations of women of reproductive age from 1988 through 1992. We calculated standardized mortality ratios, by cause, from deaths in women known to have been pregnant and deaths in same-aged women not known to have been pregnant within the same time period. Women known to have been pregnant were approximately half as likely to die as would be expected in each of two six-month time periods: from 20 weeks gestation to 42 days postpartum (SMR 0.4, 95% CI 0.3-0.5), and from 42 days to 225 days postpartum (SMR 0.5, 95% CI 0.5-0.6). Furthermore, pregnant and recently pregnant women were not more likely to die from specific causes, with the exception of diseases of the arteries, arterioles, and capillaries (SMR 3.5, 95% CI 1.3-7.7) during pregnancy or within 42 days of pregnancy termination. The only other SMR that was > 1 was for death from cerebrovascular disorders during pregnancy and up to 42 days postpartum, although not significantly so (SMR 1.4, 95% CI 0.8-2.2). No other cause-specific SMRs were > 1. Moreover, recently pregnant women were found to be much less likely to commit suicide or to be the victims of homicide. We found no empirical justification for including deaths not directly related to pregnancy in reported counts of maternal deaths for most of the causal categories we considered.