Reproductive history patterns and long-term mortality rates: a Danish, population-based record linkage study.

Background: Inconsistent definitions and incomplete data have left society largely in the dark regarding mortality risks generally associated with pregnancy and with particular outcomes, immediately after resolution and over the long-term. Population-based record-linkage studies provide an accurate means for deriving maternal mortality rate data.

Method: In this Danish population-based study, records of women born between 1962 and 1993 (n = 1,001,266) were examined to identify associations between patterns of pregnancy resolution and mortality rates across 25 years.

Results: With statistical controls for number of pregnancies, birth year and age at last pregnancy, the combination of induced abortion(s) and natural loss(es) was associated with more than three times higher mortality rate than only birth(s). Moderate risks were identified with only induced abortion, only natural loss and having experienced all outcomes compared with only birth(s). Risk of death was more than six times greater among women who had never been pregnant compared with those who only had birth(s). Increased risks of death were 45%, 114% and 191% for 1, 2 and 3 abortions, respectively, compared with no abortions after controlling for other reproductive outcomes and last pregnancy age. Increased risks of death were equal to 44%, 86% and 150% for 1, 2 and 3 natural losses, respectively, compared with none after including statistical controls. Finally, decreased mortality risks were observed for women who had experienced two and three or more births compared with no births.

Conclusion: This study offers a broad perspective on reproductive history and mortality rates, with the results indicating a need for further research on possible underlying mechanisms.