Implications of Gestational Weight Gain in Studies of Gestational Diabetes

A research article published in JAMA Pediatrics, “Associations of Maternal Diabetes and Body Mass Index With Offspring Birth Weight and Prematurity,” asserts that maternal insulin-treated diabetes and obesity in mothers with type 2 diabetes appeared to be associated with increased risks for the offspring being large for gestational age (LGA) and preterm births. Increased LGA risks were found also for mothers with diabetes with insulin treatment, with type 2 diabetes and gestational diabetes (GDM) not treated with insulin. In addition, prematurity rose for mothers with type 2 diabetes, independent of prepregnancy body mass index (BMI). Prepregnancy BMI, with no diabetes, was associated with the risk for LGA and prematurity. Large for gestational age is a stronger marker for risk of being overweight/obese in early childhood. Rates of being overweight/obese in childhood were highest in LGA children born to mothers with GDM.2 Gestational weight gain (GWG) is an important risk factor for macrosomia.3 The GWG is calculated as the difference between weight at the last prenatal visit and the prepregnancy self-reported weight. The research by Kong et al1 would have been enhanced by including the use of self-reported prepregnancy weight. In an important and significant study such as this, it would have been appropriate to indicate not only the pregravidic weight of women but also the GWG. If the GWG is not mentioned, the risks associated with it could be underestimated. The GWG may influence the grade of insulin resistance and subclinical inflammation that accompanies GDM. It is known that prepregnancy BMI is important, but perhaps it becomes even more important than the GWG. It is not certain that only nondiabetic women with an overweight prepregnancy BMI develop a GDM. It is possible that even normal-weight women before pregnancy, if they become overweight during pregnancy, can develop a GDM, which in turn may be associated with having an LGA infant. It would be appropriate to stress from the beginning of pregnancy, not only in overweight or obese women, to avoid excessive GWG to reduce the risks of GDM and morbid obesity. In these women, adequate GWG may prevent fetal overgrowth.