Pregnancy Loss and Cardiovascular Disease: A Nationwide Cohort Study

Objectives To examine how pregnancy loss influences the risk of cardiovascular disease later in life. Design Prospective historical cohort study. Setting Danish nationwide health registries. Participants All Danish women with a recorded pregnancy from 1977 to 2017. Main outcome measures Venous thromboembolism, myocardial infarction, or ischemic stroke. Results In this two-part study, part one evaluated the 20-year absolute risk of cardiovascular disease from age 40 among 596,699 women with a full registered reproductive history. Adjusting for calendar year, diabetes, autoimmune disease, live births, and education, the absolute risk of an outcome after 0 and ≥4 pregnancy losses, respectably was: venous thromboembolism 3.0% (95% CI 2.8 to 3.2%) and 5.0% (3.4 to 6.8%); myocardial infarction 1.5% (1.4 to 1.6%) and 2.4% (1.4 to 3.6%); ischemic stroke 2.0% (1.9 to 2.1%) and 2.6% (1.5 to 3.6%). Prior stillbirth increased the absolute risk of later venous thromboembolism by 1.1% (0.2 to 2.3%); myocardial infarction by 1.1% (0.3 to 2.0%). In study part two, we included 966,490 women from first pregnancy in a time-dependent Cox regression model. Adjusted for confounders, each additional pregnancy loss increased the hazard ratio of venous thromboembolism 1.10 (95% CI 1.07 to 1.13); myocardial infarction 1.12 (1.07 to 1.18); and ischemic stroke 1.10 (1.06 to 1.14). Stillbirth was strongly associated with myocardial infarction before age 40, adjusted hazard ratio of 4.60 (2.65 to 8.00). Conclusion Pregnancy loss was associated with later venous thromboembolism, myocardial infarction, and ischemic stroke. The absolute and relative risk of outcomes increased in a dose-response manner with increasing numbers of prior pregnancy losses. Stillbirth was strongly associated with myocardial infarction before age 40.