Diabetes is the leading endocrine condition that complicates pregnancy, and the incidence is rising with the obesity epidemic and advancing maternal age. It is estimated that 5 percent of pregnancies are complicated by diabetes, with the vast majority caused by gestational diabetes mellitus (GDM) and the remainder caused by type 1 or type 2 diabetes mellitus (DM).
Physiologic Changes in Pregnancy
Pregnancy is associated with accelerated starvation, which results in increased ketogenesis and lower fasting plasma glucose levels, especially in the first trimester. The increased ketogenesis predisposes mothers to episodes of diabetic ketoacidosis. In early gestation, especially during weeks 7 to 12, there may be a 10 to 20 percent drop in insulin requirements before insulin-resistant placental hormones rise. This period is associated with an increased risk of hypoglycemic episodes without autonomic warnings. Maternal hypoglycemia unawareness is an important risk factor for the development of severe hypoglycemia.
In mid to late pregnancy, increased levels of human placental lactogen (hPL), human placental growth hormone (hPGH), cortisol, and prolactin lead to an insulin-resistant state. This leads to maternal insulin resistance at the level of skeletal muscle and adipose tissue to meet metabolic fetal demands that are 80 percent derived from glucose. It is important to note that if insulin requirements decrease significantly late in gestation, it may be a sign of placental failure. Changes in therapeutic requirements in patients with diabetes should be anticipated during this time by health care providers.
Diabetes during pregnancy is associated with an increased risk of preeclampsia (15%-30%), polyhydramnios (15%-20%), and cesarean section or instrumental delivery (25%-40%).
Patients with diabetes also have important comorbidities that may need to be addressed during pregnancy, such as hypertension and obesity. There is evidence of an increased risk of progression of retinopathy and nephropathy.
Maternal hypoglycemia and unawareness
Uncontrolled maternal hyperglycemia
Severe fetal macrosomia
Polyhydramios and progressive growth restriction
Women with type 1 diabetes are at increased risk of diabetic ketoacidosis (DKA) during pregnancy because of increased ketogenesis, chronic compensated respiratory alkalosis and thus lower buffering capacity, increased rates of infection, and use of corticosteroids for fetal lung maturation. DKA most commonly occurs in the second or third trimesters. Although the presentation is similar to that in nonpregnant patients, glucose levels may be much lower, and the acidosis more pronounced. Ketones readily cross the placenta, and DKA is associated with high fetal mortality. Treatment is the same as in nonpregnant patients and requires prompt recognition, intravenous (IV) rehydration, electrolyte replacement, and IV insulin therapy. Identification of the triggering condition is crucial. Concise guidelines on the treatment of DKA in pregnancy are available.
Intrapartum Management of Diabetes
Timing and Mode of Delivery