Pregnancy is associated with increased tissue resistance to insulin, resulting in increased levels of blood insulin as well as glucose and triglycerides. These changes are due to placental lactogen and elevated circulating estrogens and progesterone. Although pregnancy does not appear to alter the long-term consequences of diabetes, retinopathy and nephropathy may first appear or become worse during pregnancy. Debate continues over whether gestational diabetics are women whose glucose intolerance is solely a function of their pregnant compared with their nonpregnant state. Alternatively, pregnancy may merely serve to unmask an underlying propensity for glucose intolerance, which will be evident even in the nonpregnant state at some time in the future if not in the immediate postpartum period. However, goals for glycemic control during pregnancy are the same whether the diagnosis is made before or during the pregnancy.
Prepregnancy counseling and evaluation of diabetic women should include a complete chemistry panel, HbA1c determination, 24-hour Urine collection for total protein and creatinine clearance, funduscopic examination, and an ECG. Any medical problems should be addressed, and HbA1c levels of less than 8% should be achieved before pregnancy. Euglycemia should be established before conception and maintained during pregnancy with daily home glucose monitoring by the patient. A well-planned dietary program is a key component, with an intake of 1800-2200 kcal/d divided into three meals and three snacks. Insulin is given subcutaneously in a split-dose regimen with frequent dosage adjustments. Patients taking oral agents prior to pregnancy should be switched to insulin. However, limited information suggests that agents such as glyburide may be safe and effective in pregnancy. The use of continuous insulin pump therapy has been found to be very useful during pregnancy in women with type 1 diabetes mellitus.
Congenital anomalies result from hyperglycemia during the first 4-8 weeks of pregnancy. They occur in 4-10% of diabetic pregnancies (two to three times the rate in nondiabetic pregnancies). Euglycemia in the early weeks of pregnancy, when organogenesis is occurring, reduces the rate of anomalies to near-normal levels. Even so, because few women with diabetes begin a rigorous program to achieve euglycemia until well after they have become pregnant, congenital anomalies are the principal cause of perinatal fetal deaths in diabetic pregnancies. All women with diabetes should receive counseling about pregnancy and, when the decision has been made to start a family, should receive prepregnancy management by physicians experienced in diabetic pregnancies.
Fasting and preprandial glucose values are lower during pregnancy in both diabetic and nondiabetic women. Euglycemia is considered to be 60-80 mg/dL while fasting and 30-45 minutes before meals and < 120 mg/dL 2 hours after meals. This is the target for good diabetic control during pregnancy. Glycated hemoglobin levels help determine the quality of glucose control both before and during pregnancy.
While perinatal problems for mother and baby are decreased by fastidious diabetic control, the incidence of hydramnios, preeclampsia-eclampsia, infections, and prematurity is increased even in carefully managed diabetic pregnancies. Diabetes is an inherently unstable disease characterized by fluctuations of blood glucose levels, particularly late in pregnancy. The risk of fetal demise in the third trimester (stillbirth) and neonatal death increases with the level of hyperglycemia. Consequently, pregnant women with diabetes must receive regular antepartum fetal testing (nonstress testing, contraction stress testing, biophysical profile) during the third trimester. The timing of delivery is dictated by the quality of diabetic control, the presence or absence of medical complications, and fetal status. The goal is to reach 39 weeks (38 completed weeks) and then proceed with delivery. Confirmation of lung maturity is necessary only for delivery prior to 39 weeks. Cesarean sections are performed for obstetric indications.
Because 15% of patients with gestational diabetes require insulin during pregnancy and because the infants of gestational diabetics have some risks similar to those of infants of diabetic mothers (particularly macrosomia), screening of women for glucose intolerance has been recommended between the 24th and 28th weeks of pregnancy (Table 18-3). Patients with gestational diabetes should be evaluated 6-8 weeks postpartum by a 2-hour oral glucose tolerance test (75 g glucose load).
ACOG Practice Bulletin. Clinical management guidelines for obstetrician-gynecologists. Number 30, September 2001. Gestational diabetes. Obstet Gynecol 2001;98:525.
Gabbe SG et al: Benefits, risks, costs and patient satisfaction associated with insulin pump therapy for the pregnancy complicated by type 1 diabetes mellitus. Am J Obstet Gynecol 2000;182:1283.
Langer O et al: A comparison of glyburide and insulin in women with gestational diabetes mellitus. N Engl J Med 2000; 343:1134.
Temple R et al: Association between outcome of pregnancy and glycaemic control in early pregnancy in type I diabetics: population based study. BMJ 2002;325:1275.
Revision date: June 21, 2011
Last revised: by Jorge P. Ribeiro, MD