Obesity and risk of stillbirth, infant death

Women who are obese before becoming pregnant seem to have a higher risk of stillbirth and of having an infant die soon after birth.Researchers from the Aarhus University Hospital, Denmark, studied more than 24,000 Danish women and found that compared to normal-weight women, those who were obese before pregnancy had twice the risk of stillbirth and to have a baby die within a month. For all of the women regardless of weight, stillbirths and newborn deaths were relatively uncommon. Among obese women, stillbirths occurred at a rate of less than 12 per 1,000 births, and the rate of newborn death was lower at about 7 per 1,000 births. But the figures compare with a stillbirth rate of 4 per 1,000 births among normal-weight women and a newborn death rate of less than 3 for every 1,000 births. Women who were overweight but not obese had risks comparable to those of normal-weight women.

The data suggest that obesity is associated with a marked increased risk of stillbirth and neonatal deaths, emphasizing the need for public health interventions to prevent obesity in young women.The study is not the first to link obesity to greater odds of stillbirth and newborn death. In the past, researchers have found that the risks may be partially explained by the higher rates of diabetes and high blood pressure seen in overweight pregnant women. But in this study, diabetes and high blood pressure were not key factors. When the researchers excluded women with either of the two disorders from their analysis, the risks of stillbirth and newborn death linked to obesity remained essentially unchanged.

Overall, the researchers found, no single cause of stillbirth or newborn death explained the higher rates among obese women. Compared with their normal-weight and overweight counterparts, obese women had a higher rate of stillbirths classified as unexplained and problems with the placenta - which transfers oxygen and nutrients from the mother's blood to the fetus - were more common.Exactly why obesity may raise the risk of stillbirth and early infant death is not clear, but the researchers point out that obesity is known to affect the hormonal system and the metabolism of blood fats. High cholesterol, they note, may affect certain substances in the body that control blood clotting and blood vessel dilation, and thereby impair blood flow to the placenta.
While the ultimate goal is to prevent obesity in the first place, the researchers add that referring more obese women to obstetricians who specialise in high-risk pregnancies could potentially reduce the fetal and newborn deaths.

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