Approximately 1% of all pregnant patients are diabetic before pregnancy. Type 2 pregestational diabetes mellitus is most common. Although 90% of diabetes cases encounteredduring pregnancy are GDM, more than one half of these even-tually develop type 2 pregestational diabetes mellitus later in life.
Women with pregestational diabetes should receive an ultrasound examination early in pregnancy to check for fetal viability and accurately date the gestational age. At 18 to 20 weeks of gestation, an ultrasound examination that focuses on identification of congenital anomalies, es-pecially those of the heart and great vessels, is indicated. Echocardiography may also be done if there are suspected cardiac defects or when the fetal heart and great vessels could not be visualized by ultrasonography.
Antepartum fetal monitoring, including fetal movement counting, the nonstress test, biophysical profile, and contraction stress test, performed at appropriate intervals, is a valuable approach and can be used to monitor women with pregestational diabetes. This testing is usually initiated at 32 to 34 weeksof gestation, but can be undertaken earlier if other high-risk conditions exist.
Pregnant patients with pregestational diabetes, especially type 1 diabetes, are at higher risk for diabetic ketoacidosis (DKA), the management of which is not altered in preg-nancy. Fetal death can accompany DKA, so electronic fetal monitoring is essential until the maternal metabolic status is stabilized.
Hypoglycemia may also occur periodically, especiallyearly in pregnancy, when nausea and vomiting interfere with caloric intake. Although hypoglycemia does not have adverse effects on the fetus, patients and family should be taught how to respond quickly and appropriately to hypoglycemia.
In addition to the added difficulties of glucose man-agement and the increased risk of DKA during pregnancy, mothers with pregestational diabetes have a two-fold increase in the incidence of pregnancy-induced hypertension, or preeclamp-sia, compared with patients without diabetes. Because of thisincreased risk of preeclampsia, 24-hour urine collections to determine the level of proteinuria and creatinine clear-ance are often used in pregestational diabetics. Additionally, if patients have preexisting diabetic nephropathy, man-ifested by pre-pregnancy creatinine >1.5 or severe pro-teinuria, they are at an increased risk of progression to end-stage renal disease, and serial monitoring of renal function is warranted.
Diabetic retinopathy worsens in approximately 15% of pregnant patients with preexisting diabetes, some pro-ceeding to proliferative retinopathy and loss of vision if the process remains untreated by laser coagulation. Therefore, women with pregestational type 1 or type 2 diabetes should have an ophthalmologic evaluation once in their first trimester if asymptomatic, and as needed if symptoms arise.
The patient with long-standing diabetes should realize that strict control of her glucose levels is advised during pregnancy, with greater attention to and more frequent monitoring of glucose values. For these patients, manage-ment ideally begins before conception, with the goal of optimal glucose control before and during pregnancy. Hemoglobin A1clevels can be measured to reflect average glucose values over the preceding 12 weeks. These levels can then be used to monitor glucose control both before and during preg-nancy and to predict the likelihood of congenital anom-alies in the fetus.
Excellent glucose control is achieved using a careful combination of diet, exercise, and insulin therapy. Insulinrequirements will increase throughout pregnancy, most markedly in the period between 28 to 32 weeks of gestation.
The impact of pregnancy on diabetes, and vice versa, must also be emphasized to the pregnant patient with pre-gestational diabetes. Patients may need to be seen every 1 to 2 weeks during the first two trimesters and weekly after 28 to 30 weeks of gestation.