Scheduling birth before a mother's due date may prevent preeclampsia

By American Heart Association News

John Fedele/Tetra Images via Getty Images
(John Fedele/Tetra Images via Getty Images)

More than half of all preeclampsia cases that occur near the end of pregnancy may be prevented by inducing birth or delivering the baby by cesarean section in the final weeks, new research suggests.

The study, which relied on computer modeling to predict risk, was published Monday in the American Heart Association journal Hypertension.

Preeclampsia is a dangerous condition characterized by high blood pressure and protein in the urine. It affects 1 in 25 pregnancies in the United States. A woman is diagnosed with preeclampsia if her systolic blood pressure (the top number) is 140 mmHg or higher or her diastolic (bottom number) is 90 mmHg or higher during pregnancy. It is typically diagnosed after 20 weeks and is a leading cause of maternal death worldwide. There are no known strategies for effectively preventing this condition.

Symptoms of preeclampsia may include headaches, vision changes and swelling in the mother's hands, feet, face or eyes. It may also cause changes in the baby's well-being. Women who develop this condition during pregnancy face an increased risk for heart problems later in life.

Most preeclampsia diagnoses are "at term," meaning they occur between 37 and 42 weeks of pregnancy. Low-dose aspirin can reduce the risk of developing preeclampsia earlier in pregnancy by more than half in women at risk, but that does not reduce the risk at the end of a pregnancy, when preeclampsia is three times more likely to occur. At-term preeclampsia is associated with more complications than when the condition develops earlier.

Researchers analyzed more than 10 years of health records related to nearly 90,000 pregnancies at two hospitals in the United Kingdom. They included data on when and how participants' babies were delivered. The majority of the women in the study were in their early 30s, white and at the upper limits of a normal weight.

Regardless of whether they were screened in the first or third trimester, women were diagnosed with at-term preeclampsia with similar frequency.

The analysis found that when a computer program – one that predicts the risk of preeclampsia based on factors such as maternal history, blood pressure, ultrasound and blood tests – was used in place of standard clinical screening, inducing a birth or delivering by C-section would reduce the risk of at-term preeclampsia by more than half.

"Timed birth is achievable in many hospitals or health centers," lead study author Dr. Laura A. Magee said in a news release. She is a professor of women's health at King's College in London. "Our proposed approach to prevent at-term preeclampsia has huge potential for global good in maternity care."

Importantly, she said, "being at higher risk of at-term preeclampsia was associated with earlier spontaneous onset of labor, so women at the highest risk were already less likely to deliver close to their due date."

In a 2023 scientific statement about optimizing heart health before pregnancy, the AHA encouraged women to eat a healthy diet, not smoke and maintain a healthy weight to reduce the risk for preeclampsia and other pregnancy complications.

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