Diabetes is the leading endocrine condition complicating pregnancy, with rising incidence due to 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) followed by type 1 or type 2 diabetes mellitus (DM).
Physiologic Changes in Pregnancy
Pregnancy is associated with accelerated starvation, resulting in increased ketogenesis and lower fasting plasma glucose levels, most pronounced in the first trimester. The increased ketogenesis predisposes mothers to episodes of diabetic ketoacidosis. In early gestation, especially weeks 7 to 12, there may be a 10 to 20 percent drop in insulin requirements before insulin-resistant placental hormones rise. Impaired counterregulatory hormone responses (specifically epinephrine and growth hormone) also occur in pregnancy. This period is thus associated with an increased risk of hypoglycemic episodes without autonomic warning. 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 maternal insulin resistance at the level of skeletal muscle and adipose tissue facilitates 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 insufficiency. 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 also evidence of an increased risk of progression of retinopathy and nephropathy.
Maternal hypoglycemia and unawareness
Uncontrolled maternal hyperglycemia
Severe fetal macrosomia
Polyhydramnios and progressive growth restriction
Women with diabetes are at increased risk of diabetic ketoacidosis (DKA) during pregnancy due to increased ketogenesis, impaired buffering capacity of the chronically compensated respiratory alkalotic state, and maternal insulin resistance mid-to-late pregnancy. It is most often associated with type 1 DM; however, has been recognized in type 2 DM and GDM. Common triggers include protracted vomiting, hyperemesis gravidarum, infections, nonadherence to insulin or insulin pump failures, and use of corticosteroids for fetal lung maturation. DKA most commonly occurs in the second or third trimester. 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 ...