Pregnancy and Future Maternal Cardiovascular Disease Risk in the HUNT Study: A Life Course Perspective

Abstract

Background: Pregnancy may be an ideal “window” into future cardiovascular health. During pregnancy, there are massive changes to the cardiovascular system which may directly alter a woman’s physiology. These changes may also provide insight into how a women responds to physiological stress, with pregnancy complications considered a “failed stress test”. Objectives: We investigated 1) the long-term effect of pregnancy on lipid levels, 2) whether preterm delivery (the most common pregnancy complication) was associated with differences in established cardiovascular risk factors both before and after pregnancy, and 3) whether pregnancy complications improved prediction of cardiovascular disease (CVD) events above-and-beyond established risk factors. Study Population: We used linked data from the population-based HUNT study, the Medical Birth Registry of Norway, validated hospitalizations, and the Norwegian Cause of Death Registry. This combination of registry data on pregnancy complications, fatal and nonfatal CVD endpoints, and clinically measured CVD risk factors and biosamples provided a unique environment to examine pregnancy and cardiovascular disease risk. Results: We found adverse changes in lipids following a first birth which persisted for decades, setting women who bore children on a more atherogenic trajectory compared to women who remained nulliparous throughout their life. Although previous studies identified an increased risk of CVD among women who had a preterm delivery, we did not find differences in life course CVD risk factor trajectories that would explain the increased risk in this group. We also did not find that adding a history of preterm birth and other pregnancy complications (i.e. hypertensive disorders of pregnancy and small for gestational age) improved the performance of a CVD risk prediction model currently used in clinical practice. Conclusions: Pregnancy may cause lasting adverse changes in lipids, providing insight into how “good” and “bad” cholesterol ratios develop across the life course. Although pregnancy complications can identify a group of women at high risk of CVD, women who had a preterm delivery may be too heterogenous a group to recommend a uniform approach to CVD prevention and the benefit of adding pregnancy complications to current risk prediction models for the general population may be low.