The study sheds new light on delivery timing guidelines for women with chronic hypertension

The study sheds new light on delivery timing guidelines for women with chronic hypertension

A collaborative study by medical researchers at the University of Cincinnati College of Medicine sheds new light on current delivery timing guidelines for pregnant mothers with chronic hypertension.

In a study recently published in the journalO&G openResearchers found that 39 weeks of pregnancy is optimal for delivery when chronic high blood pressure is a factor.

Current recommendations advocate delivery between 37 and 39 weeks, but these guidelines are based on limited evidence. This unique study used a national, current patient data set to show why 39 weeks is optimal.

The researchers used birth data from the U.S. Centers for Disease Control and Prevention from 2014 to 2018, which included about 227,000 women. This was the largest study to date to examine the timing of delivery in pregnant mothers with chronic hypertension.

"This study is broadly relevant because it used a large data set that included all births in the United States during the given time period to provide data-driven recommendations for timing of delivery in women with chronic hypertension," said corresponding author Robert Rossi, MD, associate professor in the Department of Obstetrics and Gynecology and director of the Division of Maternal-Fetal Medicine, a specialty that focuses on the treatment of high-risk pregnancies.

Data shows that 3 to 10% of pregnant women have high blood pressure, a vascular disease that affects blood flow to the uterus and placenta and can affect the growth of a fetus. Chronic hypertension can lead to preeclampsia, premature birth, stillbirth, low birth weight, and neonatal death after delivery.

Rossi said her study provides evidence that women with chronic high blood pressure should not remain pregnant beyond 39 weeks of pregnancy - but may also benefit from avoiding preterm birth, defined as before 39 weeks of pregnancy, in the absence of other adverse circumstances.

The study concluded that in patients with chronic hypertension, delivery at 39 weeks provides the optimal balance between the risk of stillbirth associated with an ongoing pregnancy and the risk of health problems or infant death associated with delivery before 39 weeks.

The research team also found the same optimal timing of delivery in African American women, who are disproportionately affected by chronic hypertension during pregnancy and are at higher risk of stillbirth and infant death.

For about 100 patients with chronic hypertension who deliver at 39 weeks instead of 40 weeks, we would experience one fewer stillbirth, infant death, or adverse neonatal outcome.”

Robert Rossi, MD, associate professor in the Department of Obstetrics and Gynecology and director of the Division of Maternal-Fetal Medicine

Optimal timing of delivery is crucial, he explained, as the prevalence of chronic hypertension increases during pregnancy.

“In the future, it will also be important to study patients who receive medication for their chronic hypertension during pregnancy to determine whether they should also deliver at 39 weeks or whether earlier delivery is more beneficial for this particular group,” Rossi said.

Rossi's study collaborators included lead author Ira Hamilton, MD, a former UC College of Medicine fellow in maternal-fetal medicine who now practices in the Toledo area; Emily DeFranco, DO, former director of the UC Division of Maternal-Fetal Medicine, now chair of obstetrics and gynecology at the University of Kentucky College of Medicine; James Liu, MD, another former UC maternal-fetal medicine fellow who now practices in Colorado; and Labeena Wajahat, MD; a former UC obstetrics and gynecology doctor who now practices in Texas.

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