Association of Conventional Cardiovascular Risk Factors With Cardiovascular Disease After Hypertensive Disorders of Pregnancy: Analysis of the Nord-Trøndelag Health Study

Importance:
Women with a history of hypertensive disorders of pregnancy (HDP) have higher risk of cardiovascular disease (CVD). It is not known how much of the excess CVD risk in women with a history of HDP that is explained by conventional cardiovascular risk factors.

Objective:
To quantify the excess risk of CVD in women with a history of HDP and estimate the proportion explained by conventional cardiovascular risk factors.

Design:
Prospective cohort study with a median follow-up of 18 years.

Setting:
Population-based cohort of women participating in the Nord-Trøndelag Health Study (HUNT) in Norway.

Participants:
We linked data for 31 364 women from the HUNT Study to validated hospital records, the Cause of Death Registry and the Medical Birth Registry of Norway. 7399 women were excluded based on selected pregnancy characteristics, incomplete data or because of emigrating or experiencing the end-point before start of follow-up, leaving 23 885 women for study.

Exposure:
Experiencing one or more pregnancies complicated by hypertensive pregnancy disorder before age 40 versus only experiencing normotensive pregnancies.

Main Outcomes and Measures:
We used Cox proportional hazards models to estimate the hazard ratios for the association between HDP and CVD. The proportion of excess risk explained by conventional cardiovascular risk factors was estimated using an inverse odds ratio weighting approach.

Results:
A total of 21 766 women had only normotensive pregnancies, while 2199 women experienced ever having a hypertensive pregnancy disorder. From age 40 to 70, women with history of HDP had an increased risk of CVD compared to women with only normotensive pregnancies (HR=1.57, 95% confidence interval: 1.32–1.87), but not at older age (p for interaction by age=0.015). Blood pressure and BMI accounted for up to 77% of the excess risk of CVD in women with history of HDP, while glucose and lipids accounted for smaller proportions.

Conclusion and Relevance:
The excess risk of CVD in women with history of HDP is largely explained by conventional cardiovascular risk factors, indicating that these risk factors are important targets for cardiovascular prevention in these women.