Hypertensive Disorders of Pregnancy, Preterm Delivery, and Infant Size: Which Mothers Have Highest Cardiovascular Disease Mortality?

BACKGROUND: Research on new-onset hypertensive disorders of pregnancy (HDP) and long-term maternal cardiovascular disease (CVD) death has focused on mothers of small-for-gestational-age infants rather than large-for-gestational-age infants. OBJECTIVES: We further explored this focus by investigating CVD death in mothers with HDP by gestational age at delivery across the full spectrum of infant birth size. METHODS: We used data from the Medical Birth Registry of Norway, the Norwegian National Population Register, and the Norwegian Cause of Death Registry, with information on mothers giving birth 1967-2020. This data was used to predict CVD death in the decades following pregnancy. RESULTS: We found the lowest CVD mortality among mothers with no HDP, term delivery, and a first infant with birthweight above average. These women constituted our reference group in the analyses. We found the highest risk of CVD death among mothers with preterm HDP and infants with above average birthweight for gestational age (HR 6.87, 95% CI 4.98, 9.48), not with infants below average birthweight for gestational age (HR 3.06, 95% CI 2.37, 3.93). CONCLUSIONS: There is an interactive association between HDP and large infant birthweight in preterm first births. The high risk associated with the particular combination of HDP, preterm birth, and high infant birthweight for gestational age warrants further research to understand its causal underpinnings.