According to a study published in The Journal of Physiology, maternal obesity during pregnancy can result in negative or fatal outcomes for both the mother and the baby. The study showed that excess weight alters the structure of the placenta more than poor glucose control in pregnancy.

Globally, the prevalence of both, gestational diabetes, or low blood sugar during pregnancy, and obesity is rising. Although both have been associated with a number of maternal and fetal problems, including an increased risk of stillbirth, infant death, and low birth weight, their exact causes are still unknown.

The study found that maternal obesity, more so than gestational diabetes, decreased the placentas capacity to exchange nutrients between the mother and growing child as well as the density and surface area of its blood vessels. Inflammation indicators and placental hormone synthesis are both impacted by gestational diabetes and obesity, indicating that the placenta is really operating improperly.

Professor Mushi Matjila from the University of Cape Town stated that the study "highlighted the importance of obesity over gestational diabetes in modulating placental structure and function." He added that identifying specific changes in the placenta can pave the way for developing new therapies and screening procedures that specifically target the placenta and aim to improve maternal and foetal health, especially in low- and middle-income nations. 

(Source: https://www.tribuneindia.com/news/health/obesity-in-pregnancy-more-deadly-for-mother-baby-study-483835 )