I. DIABETES AND PREGNANCY OUTCOME. Improved management of diabetes mellitus and advances in obstetrics have reduced the incidence of adverse perinatal outcome in pregnancies complicated by diabetes mellitus. With appropriate management, women with good glycemic control and minimal microvascular disease can expect pregnancy outcomes comparable to the general population. Women with advanced microvascular disease, such as hypertension, nephropathy, and retinopathy, have a 25% risk of preterm delivery because of worsening maternal condition or preeclampsia. Pregnancy does not have a significant impact on the progression of diabetes. In women who begin
pregnancy with microvascular disease, diabetes often worsens, but in most, the disease return to baseline. Preconception glucose control may reduce the rate of complications to as low as that seen in the general population.

1. Diabetes that antedates the pregnancy can be associated with adverse fetal and maternal outcomes. The most important complication is diabetic embryopathy resulting in congenital anomalies. Congenital anomalies are associated with 50% of perinatal deaths among women with diabetes compared to 25% among nondiabetic women. The risk of congenital anomalies is related to the glycemic profile at the time of conception. The most common types of anomalies include cardiac malformations and neural tube defects. Women with type 1 and type 2 diabetes are at significantly increased risk for hypertensive disorders, such as preeclampsia, which is potentially deleterious to both maternal and fetal well-being. Gestational diabetes mellitus (GDM) is defined as carbohydrate intolerance of variable severity first diagnosed during pregnancy, and it affects 6% to 8% of pregnancies.

2. Epidemiology of gestational diabetes. Approximately 3% to 5% of patients with GDM actually have underlying type 1 or type 2 diabetes, but pregnancy is the first opportunity for testing. Risk factors for GDM include advanced maternal age, multifetal gestation, increased body mass index, and strong family history of diabetes. Certain ethnic groups, such as Native Americans, Southeast Asians, and African Americans, have an increased risk of developing GDM.

3. Physiology unique to women with diabetes antedating pregnancy. In the first half of pregnancy, as a result of nausea and vomiting, hypoglycemia can be as much of a problem as hyperglycemia. Hypoglycemia, followed by hyperglycemia from counter-regulatory hormones, may complicate glucose control. Maternal hyperglycemia leads to fetal hyperglycemia and fetal hyperinsulinemia, which results in fetal overgrowth. Gastroparesis from long-standing diabetes may be a factor as well. There does not appear to be a direct relationship between hypoglycemia alone and adverse perinatal outcome. Throughout pregnancy, insulin requirements increase because of the increasing production of placental hormones that antagonize the action of insulin. This is most prominent in the mid-third trimester and requires intensive blood glucose monitoring and frequent adjustment of medications to control blood glucose.

1. Ketoacidosis is an uncommon complication during pregnancy. However, ketoacidosis carries a 50% risk of fetal death, especially if it occurs before the third trimester. Ketoacidosis can be present in the setting of even mild hyperglycemia (200 mg/dL) and should be excluded in every patient with type 1 diabetes who presents with hyperglycemia and symptoms such as nausea, vomiting, or abdominal pain.

2. Stillbirth remains an uncommon complication of diabetes in pregnancy. It is most often associated with poor glycemic control, fetal anomalies, severe vasculopathy, and intrauterine growth restriction (IUGR) as well as severe preeclampsia. Shoulder dystocia that cannot be resolved can also result in fetal death.

3. Polyhydramnios is not an uncommon finding in pregnancies complicated by diabetes. It may be secondary to osmotic diuresis from fetal hyperglycemia. Careful ultrasonographic examination is required to rule out structural anomalies, such as esophageal atresia, as an etiology, when polyhydramnios is present.

4. Severe maternal vasculopathy, especially nephropathy and hypertension, is associated with uteroplacental insufficiency, which can result in IUGR, fetal intolerance of labor, and neonatal complications.