While obese women face an increased risk of stillbirth, that risk skyrockets in late pregnancy for extremely obese women, concludes a new study published online in the American Journal of Obstetrics & Gynecology. Researchers looked at data on 2,868,482 singleton pregnancies in Texas and Washington state from 2003 to 2011 and assessed the risk of stillbirth by the women's obesity rate at each of four gestational periods: 30-33, 34-36, 37-39 and 40-42 weeks. They found that in each progressive period, the risk of stillbirth grew with women's increasing body mass index. However, while stillbirth risk increased gradually for moderately overweight women, the risk increased sharply in late pregnancy for class III obese (BMI of 40.0 to 49.9 kg/m2) women and those with a BMI of 50.0 kg/m2 or more. For these women, the risk of stillbirth was 40% and 69% greater, respectively, at 30-33 weeks, compared to normal-weight women, but at 40-42 weeks, their risk grew to more than threefold and nearly ninefold, respectively. Obesity was associated with nearly 25% of stillbirths that occurred between 37 and 42 weeks. Read the abstract.