Obese women who undergo rapid weight loss to get pregnant may harm rather than improve their chances of having a healthy baby, a leading researcher suggested this week. Professor Richard Legro of the Department of Obstetrics and Gynecology at Penn State University College of Medicine, Hershey, Pennsylvania, USA, said the subject was under-researched and outcomes unknown. But he pointed out that sudden and dramatic reductions in calories and increases in activity during the periconceptual period in all women, including those undergoing assisted reproduction techniques (ART), could have potentially adverse effects. Weight-loss interventions put stress on the reproductive system that could lead to failure through a variety of mechanisms, he warned.

Apart from disruption to normal physiological mechanisms, an additional concern hypothesised is that environmental pollutants stored in fat such as DDT and organochlorine, released into the blood circulation when fat is metabolised during lifestyle interventions, could have potentially adverse effects on the pregnancy.