High BP Early in Pregnancy Linked to Birth Risks

Marcia Frellick
June 27, 2019

High blood pressure during the first trimester of pregnancy, or an increase in blood pressure between the first and second trimesters, is linked to higher risk for gestational hypertension and preeclampsia, a study indicates.

Both conditions heighten the risk for maternal stroke as well as for premature birth, stillbirth, and low birthweight. Preeclampsia also increases the mother's risk for life-threatening seizures, the authors write.

"We compared the frequency of hypertensive disorders of pregnancy, including preeclampsia and gestational hypertension, among women based on ACC/AHA [American College of Cardiology/American Heart Association] blood pressure category at a first trimester study visit and blood pressure trajectory between study visits in the first and second trimesters," they explain.

The findings by Alisse Hauspurg, MD, with the Magee-Womens Research Institute at University of Pittsburgh School of Medicine in Pennsylvania, and colleagues suggest that this study may identify otherwise "low-risk" women who may be at risk for a hypertensive disorder of pregnancy (HDP).

The study was published online June 27 in the American Journal of Obstetrics and Gynecology.

In 2017, the ACC/AHA recategorized blood pressure levels and lowered the threshold for a diagnosis of chronic hypertension. Hauspurg and colleagues wanted to study the new guidelines' relevance for pregnant women.

"Considering that the prevalence of pre-gestational hypertension has been projected to double in women newly-designated as having hypertension based on the new ACC/AHA guidelines, understanding risk in this group is particularly relevant for clinicians," the authors write.

Among women who had elevated blood pressure in the first trimester (120/80 to 129/80 mmHg), 30.3% developed an HDP, which represents a 42% higher risk than for women with normal blood pressure. Of women with stage 1 hypertension (130/80 to 130/89 mmHg), 37.8% developed an HDP, a risk 80% higher than that of women with normal blood pressure. Stage 1 hypertension was linked with more than 2.5 times the risk for preeclampsia with severe features (adjusted relative risk, 3.48; 95% confidence interval, 1.38 – 8.74).

An increase in blood pressure between the first and second trimesters also raised the risk for a hypertensive disorder. Even for women whose blood pressure was normal during the first trimester, an increase in systolic blood pressure during in the second trimester raised the risk for a hypertensive disorder by 41% compared with women whose systolic pressure went down during that period. If the diastolic pressure went up, the risk was 23% higher compared with those whose diastolic pressure decreased during that time.

The researchers used data from the Nulliparous Pregnancy Outcomes Study: Monitoring Mothers-to-Be cohort, a prospective observational study of women who had not previously given birth and who had single pregnancies at eight clinical sites between 2010 and 2014. The 8899 women who were included had no known history of prepregnancy hypertension or diabetes.

The authors hope the study will spur further research in hypertension among pregnant women.

"Further study to identify the efficacy of additional surveillance and potential risk-reducing interventions, such as low-dose aspirin, is needed in this population," they write.

The study was funded by the Eunice Kennedy Shriver National Institute of Child Health and Human Development, part of the National Institutes of Health. The authors have disclosed no relevant financial relationships.

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SOURCE: Medscape, June 27, 2019. Am J Obstet Gynecol. Published online June 27, 2019.

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