The planned birth, by induction or caesarean section, can prevent more than half of preeclampsia cases annually that occurs in full-term pregnancy, according to research published in the American Heart Association’s journal Hypertension.

Preeclampsia is the most dangerous form of high blood pressure during pregnancy and the leading cause of maternal mortality worldwide. The condition is usually diagnosed after 20 weeks of pregnancy.

Planned delivery, by induction or caesarean section, is already widely practiced for a variety of reasons, but is rarely considered as an intervention to prevent preeclampsia in term pregnancy. Preterm delivery may be considered an option for women who develop preeclampsia during weeks 20-36 of gestation. However, in most cases preeclampsia occurs in the last weeks of pregnancy (37-42 weeks). While screening for preeclampsia is routine during pregnancy, there are limited treatment options that are proven safe and effective. Low-dose aspirin more than halves the risk of early preeclampsia among at-risk women, but has no effect on the risk of preeclampsia in full-term pregnancies, which is three times more common than preeclampsia at 20-36 weeks.

The researchers examined medical records for more than ten years for nearly 90,000 pregnancies in two UK hospitals. They assessed the risk of preeclampsia and the potential benefits of planned delivery using standard clinical criteria for preeclampsia and a risk prediction model based on factors such as maternal history, blood pressure, ultrasound and blood tests. The majority of women were in their early 30s, self-identified as white, and had a body mass index in the upper range of normal. About 10% self-identified as smokers, less than 3% had a medical history of high blood pressure, type 2 diabetes, or autoimmune disease, and only 3.9% reported a family history of preeclampsia. On average, the women in the study gave birth at 40 weeks, and two-thirds of all participants had an unplanned onset of labor. About a quarter had a caesarean section.

According to the analysis, planned delivery may prove to be an effective intervention to more than halve the risk of preeclampsia in the final weeks of pregnancy.

Limitations of the study note that the possibility of post-partum pre-eclampsia was not examined and also that the researchers only estimated the potential risk through risk modelling.

In February 2023, the American Heart Association published a scientific statement detailing the benefits of early interventions to support cardiovascular health before and during pregnancy. These interventions are related to diet, smoking cessation, weight reduction and can reduce the incidence of adverse pregnancy outcomes at birth.