In 2009, there were about 2.6 million third-trimester stillbirths worldwide. Each year, about 3.6 million infant deaths occur within 28 days of a child’s birth. A new study by researchers at Imperial College London has found that a mother's body mass index (BMI) may play a role.

The researchers discovered that women who had a high BMI score before they became pregnant or during the early phases of their pregnancies ran a higher risk of stillbirth, fetal death, and infant death. Women who were severely obese had the greatest risk, according to the study, published in the Journal of the American Medical Association.

Numerous studies have suggested a link between high BMI and infant deaths, but this one found a significant association.

Imperial College London's Dagfinn Aune, M.S., and his team reviewed all of the available data and performed a meta-analysis to find a link between BMI and the risk of these serious pregnancy complications. They included information on more than 10,147 fetal deaths, more than 16,274 stillbirths, more than 4,311 perinatal deaths, 11,294 neonatal deaths, and 4,983 infant deaths.

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Severely Obese Women Run the Highest Risk

According to Aune’s team, even a modest rise in BMI increased the risk of fetal and infant death. Severely obese women—those with a BMI greater than 40—had a twofold to threefold increase in these outcomes, compared with women who had a BMI of 20, which is within normal range.

Women who are overweight or obese also have a greater risk for gestational diabetes, gestational hypertension, and preeclampsia. They are also at a higher risk of giving birth to a child with congenital anomalies.

Aune pointed out that the studies in the review only assessed BMI during a limited time: before or very early in pregnancy—before the pregnancy would have affected the weight of the mother to any significant degree.

“We don't have enough studies to say whether limiting the weight gain of the mothers during the pregnancy will have an impact on the stillbirth risk, but this will be of great interest for future studies to look into,” Aune said, suggesting that the scientific community look into how exercise and diet affect stillbirth risk or change the effects of obesity on stillbirth risk.

Some data show that exercise can lower the risk of pregnancy complications, such as gestational diabetes and preeclampsia. “But for stillbirth we don't have an answer yet,” Aune said.

Aune also mentioned other studies that show weight gain after one pregnancy can elevate the risk of having a stillbirth in a second pregnancy. Women may be able to lower the risk for stillbirth or infant death by preventing excess weight gain prior to a second pregnancy.

Weight Management Is Vital

Dr. Taraneh Shirazian, an assistant professor in the obstetrics, gynecology, and reproductive science department at the Icahn School of Medicine at Mount Sinai Hospital, who also heads the Global Health program at Mount Sinai, said that weight management before pregnancy is important, as is controlling weight gain during pregnancy, especially for women who have a BMI greater than 30.

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Lifestyle changes to prevent excess weight gain may lower the risk of other complications, said Shirazian. Weight management should be specific for each woman, and each woman should take into account her pregnancy history, medical conditions, and current weight.

Shirazian runs an initiative known as the Lifestyle Modification Program at Mount Sinai, and she recently conducted a study on 60 women enrolled in an educational intervention program. Shirazian believes these types of programs may be useful in helping women limit weight gain during pregnancy.

Dr. Joanne Stone, director of Maternal and Fetal Medicine at Mount Sinai, said that it’s important for women to know about the risks of high BMI during pregnancy.

“Optimizing their weight prior to becoming pregnant would give [women] the best outcome,” Stone said.

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