Impact of female obesity and assisted reproduction on uncomplicated pregnancies and healthy births: a study of 428 336 births in Flanders.

This study investigates the impact of body mass index (BMI) on pregnancy and birth outcomes in women who conceived spontaneously or via medically assisted reproduction (MAR)—including assisted reproductive technology (ART) and hormonal stimulation—in the Flanders region of Belgium. Analysis of 428,336 births from 2009 to 2015 showed that women with higher BMI who used MAR had the lowest probability of uncomplicated pregnancies and births, with risks increasing alongside BMI categories. While most women gave birth to healthy babies regardless of BMI or conception method, overweight and obese women, especially those using MAR, experienced higher rates of complications such as cesarean sections, preterm births, and large-for-gestational-age newborns. The study highlights the need for consideration of BMI in MAR-related healthcare policies and suggests that weight loss interventions prior to MAR may improve outcomes, though their effectiveness requires further research.