Pregnancy Duration and Hypertension Risk: What's the Connection?

JoAnn E. Manson, MD, DrPH


October 29, 2021

This transcript has been edited for clarity.

Hello. This is Dr JoAnn Manson, professor of medicine at Harvard Medical School and Brigham and Women's Hospital. I'd like to talk with you about an important study recently published in JAMA Cardiology on the subject of preterm delivery and long-term risk for hypertension in women. This is the largest study ever done on this subject, and it leveraged nationwide birth register data from Sweden, which included more than 2.1 million women, more than 4 million births dating back to 1973, and more than 40 years of follow-up.

They found that a preterm delivery (birth at less than 37 weeks' gestation) was a strong predictor of increased risk for hypertension in women compared with a full-term birth (39-41 weeks' gestation). Overall, there was a 67% increased risk for new-onset hypertension in this study, and the shorter the pregnancy, the greater the increase in risk. So women who had a pregnancy duration of 22-27 weeks had more than a doubling in the risk for new-onset hypertension. Women with a pregnancy duration of 28-33 weeks had an 85% increased risk for hypertension. Women with a pregnancy duration of 34-36 weeks had a 55% higher risk for hypertension and an elevation in hypertension.

Risk persisted over the full 40 years of follow-up, suggesting that preterm delivery is a predictor of an increased risk for hypertension across the life span. They did adjust for preeclampsia and pregnancy-related factors, including pregnancy-induced hypertension and other maternal factors. They even used sibling controls to adjust for any genetic and familial shared determinants of risk. Still, they continued to see that preterm delivery was associated with excess hypertension risk.

Along with evidence that preeclampsia and gestational diabetes are risk factors for future cardiovascular risk in women, these findings serve as a window into a woman's cardiovascular risk. Even irregular and long menstrual cycles (40 days or longer) should be considered a vital sign and a marker for a woman's future cardiometabolic risk.

The data strongly suggest that we should be asking our patients about pregnancy-related factors, including a history of preterm delivery. Women who have this history really should be monitored regularly for hypertension so it can be diagnosed and treated as early as possible. It's important for clinicians to be especially vigilant about lifestyle modification counseling, such as regular physical activity and a healthy diet, to prevent hypertension in these high-risk women.

Thank you so much for your attention. This is JoAnn Manson.

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