A recent study has found that women with blood pressure levels considered normal during pregnancy but without a mid-pregnancy dip in blood pressure face a significantly higher risk of developing hypertension in the five years following childbirth. These women, who make up about 12% of the population in the study, would not be flagged as high-risk under current medical guidelines, but the findings suggest that early intervention could help prevent long-term cardiovascular issues.
The study, published in the Journal of the American College of Cardiology: Advances, was funded in part by the National Institutes of Health. Researchers tracked blood pressure and other health factors in 854 women from pregnancy through five years postpartum. By taking a longitudinal approach, the study revealed a connection between certain blood pressure patterns during pregnancy and an increased risk of hypertension years later.
Of the women studied, 80.2% had consistently low systolic blood pressure throughout pregnancy. Another 7.4% showed a pattern of high blood pressure that dropped in the second trimester before rising again. The third group, accounting for 12.4%, had slightly elevated blood pressure that remained steady but did not dip during the second trimester. This group, despite having blood pressure within normal limits during pregnancy, faced a nearly five-fold increased risk of hypertension in the years following childbirth compared to women with low blood pressure throughout their pregnancies.
“This group of women would not be identified as having higher long-term hypertension risk by current clinical guidelines, as their blood pressure stayed below diagnostic thresholds,” said Shohreh Farzan, PhD, senior author of the study and associate professor at the Keck School of Medicine at USC.
The research underscores the importance of monitoring blood pressure patterns during pregnancy as a means to identify women who may be at risk for future cardiovascular issues, even if they don’t present with traditional risk factors. According to the study’s first author, Zhongzheng (Jason) Niu, PhD, this finding could help healthcare providers intervene earlier and potentially reduce the long-term risk of heart disease.
The study was part of the Maternal and Developmental Risks from Environmental and Social Stressors (MADRES) cohort, which focuses on low-income Hispanic women and their children. Researchers used latent class growth modeling to analyze blood pressure data and identify patterns over the course of pregnancy. They found that women with a mid-pregnancy drop in blood pressure, a characteristic often associated with higher-risk pregnancies, had a 5.44 times higher risk of hypertension five years after childbirth.
However, women who had slightly elevated blood pressure without a second-trimester dip were at almost the same risk, with a 4.91 times higher likelihood of developing hypertension. Because these women did not exhibit the typical risk factors, they may not be closely monitored or flagged for increased cardiovascular risk, potentially allowing hypertension to develop unnoticed.
The study is especially timely as organizations like the American Heart Association (AHA) and the American College of Obstetricians and Gynecologists are increasingly focusing on women’s heart health. After presenting the findings at the AHA EPI|Lifestyle meeting in 2023, Niu received the Trudy Bush Fellowship for Cardiovascular Disease Research in Women’s Health.
Niu emphasized the gap in research between pregnancy and menopause, a critical period in women’s health that has been historically underexplored. “Our study helps fill that gap by shedding light on hypertension risk during this overlooked window of time,” he said.
The study’s findings also suggest simple changes in clinical practice could improve outcomes for women at risk. By tracking blood pressure throughout pregnancy and following up with women who do not experience the typical second-trimester dip, healthcare providers may be able to identify and treat those at higher risk, even if their readings remain within the normal range. This could lead to better prevention of long-term cardiovascular disease.
Further research is needed to confirm these findings and to explore the potential role of environmental factors, such as air pollution and chemical exposures, in influencing blood pressure patterns during pregnancy. Farzan, Niu, and their colleagues are continuing to investigate these links as part of their ongoing work in women’s health.
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