Fetal macrosomia and shoulder dystocia in women with gestational diabetes: risks amenable to treatment?

Fetal macrosomia and maternal diabetes are independent risk factors for shoulder dystocia, an obstetrical emergency that may cause permanent neonatal injury. Randomized trials of glycemic control in pregnancies complicated by gestational diabetes reveal decreased rates of macrosomia and shoulder dystocia among those treated. However, definitions of gestational diabetes vary and a specific glycemic threshold for clinically significant risk reduction remains to be delineated. This review discusses risks associated with gestational diabetes including macrosomia (birth weight above 4000-4500 g) and delivery-related morbidity, specifically, shoulder dystocia. Subsequently, we will review recent randomized trials assessing the impact of glycemic control on these delivery-related morbidities. Finally, we will examine a large observational study that found associations with delivery-related morbidity and hyperglycemia below current diabetic thresholds, observations which may suggest reexamination of current diagnosis guidelines for gestational diabetes.