Diabetes in Pregnancy

 Men-Jean Lee, MD

(presented at the CAMS 2000 Semi-Annual Scientific Meeting)

Approximately 1/200 preg-ancies are in women with pregesational diabetes, either insulin-dependent or non-insulin dependent.  In the U.S.A., about 4% of pregnancies are diagnosed with gestational diabetes (GDM), a form of diabetes that occurs only during pregnancy and resolves after delivery of the fetus.  The prevalence of DM in the Chinese population varies from a low of 0.6% in Taiwan to a high of 13.9% in Australia. 

GDM is diagnosed by an initial screening test at 24-28 weeks of pregnancy in which a 50mg Glucola load is given and a blood glucose is drawn one hour later.  If the blood glucose is greater than 140 mg/dL, a confirmatory 3-hour glucose tolerance test is performed by drawing a fasting blood sugar, administration of a 75mg Glucola load, and testing blood glucoses at 1, 2, and 3 hours following the load.  If 2 or more values are at or above 95 (fasting), 185 (1-hour), 155 (2 hours), and 140 (3 hours), the diagnosis of GDM is made.  GDM is treated with a diabetic diet, plus or minus insulin inject-ions.  50% of women with GDM will develop overt diabetes over the next 5 years of their lives.

            Pregnancy in a woman with pregestational diabetes is a much  more serious condition.  The goal of prenatal care is to prevent maternal end-organ damage such as blindness, renal damage, and diabetic ketoacidosis; as well as to prevent fetal/neonatal complications such as miscarriage, birth defects, and growth disturbances.  Diabetic retinopathy during pregnancy can be easily diagnosed with a complete fundoscopic exam and treated with laser photocoagulation.  Diabetic nephropathy (greater than 300-500mg urine protein in 24 hours) may somewhat worsen with pregnancy.  Pregnancy should be discouraged if the patient has poor renal function or is on dialysis.   However, women with successful renal transplants do well during pregnancy.  Women with hypertension are at risk for a variety of pregnancy complications.  ACE inhibitor is contraindicated.  Beta-blockers should also be avoided.  Diabetic ketoacidosis is life-

threatening to mother and fetus with serum glucose levels as low as 200mg/dl.  Diabetics with tight glycemic control have no increase in spontaneous abortions when compared to normal women.  However, they are still at risk for having a baby with birth defects, which is increased when glucose control is worse.

Tight glycemic control with appropriate diet and insulin modifications is the mainstay of diabetes management during pregnancy.  Women need to perform home glucose monitoring at least 4 times a day with fasting blood sugar and 2-hour post-prandial blood sugars after the 3 main meals of the day.  Fasting blood sugars should be less than 95mg/dl and two-hour blood sugars less than 120mg/dl.  They should also be on a 35 kCal/kg diabetic diet.  Women are at risk for either delivering a baby with macrosomia or intrauterine growth restriction or stillbirth.  Fetal lung maturation is delayed with diabetes.  Close fetal surveillance with the assistance of a Maternal-Fetal Medicine specialist is important to detect congenital anomalies and to prevent stillbirth. #

( Dr. Lee is Assistant Profesor of Obste-trics and Gynecology at the New York University Medical School)