It turns out, there is concern about an increased risk of congenital malformations, aka birth defects. A recent study of 1.2 million pregnant women showed that the risk for specific congenital malformations increased substantially based on how obese the mother was. In this study, they assessed congenital malformations of the heart, limbs, genital organs, urinary system, digestive system, cleft lips and palates, eye, nervous system and other malformations. This was true even for women without diabetes (We'll get back to the effects of diabetes on pregnancy later). So, what did they find? The baseline risk of birth defects in normal weight mothers is 1 in 29, but this number increases to 1 in 21 for morbidly obese mothers. While the most common type of malformation noted was heart malformations, there was an increased risk of genital, urinary and nervous system malformations in obese mothers. We are not exactly sure what causes this, however, we do know that fat cells produce estrogen. There is some thought that all this extra estrogen may disrupt the signals for normal development, which in turn may contribute to an increase in congenital malformations in babies of obese moms.
Another problem for many obese moms is that increased BMI is also associated with diabetes. So, what is diabetes? THe type associated with obesity, type 2, means that your body can't process sugar well. Essentially, your body may be able to process a gummy bear, but the whole extended family of sour patch kids? Not so much. Poor control of diabetes can be teratogenic, especially in the first trimester, and can contribute to severe fetal malformation as well. This may increase the chance of having a baby with a birth defect even higher than the obesity alone. Lastly, babies born to mothers with higher BMIs have an increased chance of being obese themselves or developing diabetes later in life. Even for potentially normal babies, maternal obesity and diabetes is associated with increased chance of early pregnancy loss and stillbirth.
What it comes down to: Yes, your pre-pregnancy weight, the amount of weight that you gain during pregnancy, and the way your sugars are controlled (if you have diabetes) can have lifelong implications for your baby. Please discuss this with your provider, and let's work together to help you have your healthiest pregnancy :)