Obesity increases the risk of stillbirth, particularly during the later stages of pregnancy

The global overall risk of stillbirth in pregnancy is approximately 2.6%. Although the link between obesity and stillbirth is well-known, little research was done on the association between obesity and stillbirth risk by gestational age, or on the impact of higher classes of obesity.

For the study, researchers examined data from the Better Outcomes Registry and Network on 681,178 singleton births from 2012 to 2018, including 1,956 stillbirths and accounted for other risk factors such as diabetes and high blood pressure when analyzing the data.

The findings revealed that people with class I obesity (BMI 30–34.9 kg/m2) had double the risk of stillbirth at 39 weeks gestation compared to those with normal BMI (18.5–24.9 kg/m2). For those in obesity classes II and III (BMI 35–39.9 kg/m2 and BMI 40 kg/m2 and higher, respectively), stillbirth risk at 36 weeks was 2 to 2.5 times that of people with normal BMI. This risk further increased with gestational age, with a more than fourfold risk at 40 weeks.

The authors also explored whether stillbirths occurred before or during delivery and found a higher risk of stillbirths occurring before delivery in people with class I and II obesity.

"Our findings suggest that an earlier delivery date may help reduce the risk of stillbirth for pregnant people with obesity," says lead author Dr. Naila Ramji, a high-risk pregnancy specialist and assistant professor at Dalhousie University, with coauthors at The Ottawa Hospital. "For other medical conditions that increase the risk of stillbirth, there are guidelines that recommend delivery at 38 or 39 weeks. Interestingly, the risk thresholds for those conditions are lower than the risks we found associated with obesity. We worry that implicit biases against people with obesity may be causing the medical community to take the risks they face less seriously.”

"Pregnant people with obesity, especially those with additional risk factors may benefit from timely referral and greater surveillance closer to term, and the presence of additional risk factors may warrant earlier delivery," concluded Dr. Ramji.

Reference: Journal: Canadian Medical Association Journal; DOI: 10.1503/cmaj.221450