Current management of diabetic pregnancy

The starting dose is 2.5 mg orally in the morning. If the targeted level of glycemia is not attained, add 2.5 mg to the morning dose. If indicated (after 3 to 7 days), add 5 mg in the evening. Thereafter, increase the dose in 5-mg increments, up to a total of 20 mg per day. If the patient does not achieve acceptable glycemic control, add long-acting insulin.

Evidence on oral agents. Several retrospective and randomized studies evaluated oral agents in pregnancy. Most demonstrated that these agents are comparable to insulin in glycemic control and pregnancy outcome.^54-61

In a randomized study, my colleagues and I found comparable pregnancy outcomes for glyburide and insulin.⁵⁶ Recently we reconfirmed our original observation⁶² that hypoglycemic episodes are more common in insulin-treated patients than in those taking glyburide. In this study, we used continuous glucose monitoring and found hypoglycemic episodes in 63% of the insulin-treated women with gestational diabetes, but only in 28% of those taking glyburide.

We further analyzed the association between glyburide dose, gestational diabetes severity, and selected maternal and neonatal factors.⁶³ Not surprisingly, we found that the glyburide dose increased with the severity of gestational diabetes. The success rate (ie, achievement of glycemic control) decreased as disease severity increased. However, there was no difference between glyburide- and insulin-treated patients at each level of severity. Thus, achieving glycemic control—not any particular mode of pharmacologic therapy—is the key to improving pregnancy outcome in gestational diabetes.

When costs of insulin therapy and glyburide treatment are compared, the latter is considerably less expensive.⁶⁴

Ensuring fetal health and a safe delivery

Three principles form the basis of obstetric care for women with diabetes:

• fetal testing to prevent stillbirth and compromised fetal states at delivery,
  
• lung-maturity testing to prevent hyaline membrane disease, and
  
• determining the best time and method of delivery to prevent fetal compromise, macrosomia, and shoulder dystocia.
  

Fetal testing

At our institution, we begin fetal testing at 32 weeks’ gestation in all women regardless of diabetes type—even earlier in women with vascular/hypertensive disorders. This includes assessing fetal movements 3 times daily and nonstress testing weekly. This approach has led to a stillbirth rate of 2.5 per 1,000, compared with 4 per 1,000 in the general population.⁴

Is amniocentesis warranted to determine lung maturity?

A major goal of fetal surveillance in gestational diabetes is preventing lung disease. Inadequately controlled gestational diabetes can increase the risk of respiratory distress syndrome or delay lung maturity. Thus, assessing fetal pulmonary status by confirming gestational age or fetal size can be misleading.^65,66

The delay in lung maturity among infants of diabetic mothers is 1 to 2 weeks.⁶⁷ This delay was associated with poorly controlled diabetes in several studies. Thus, this subgroup of patients stands to benefit most from amniocentesis.

At our institution, the common practice is to test for lung maturity before any elective delivery at less than 38 weeks’ gestation. However, when the clinician determines that delivery would be beneficial, as in cases of poorly controlled diabetes, noncompliance, or other obstetric indications, we deliver the infant regardless of lung maturity. These fetuses experience minimal lung morbidity after 37 weeks’ gestation.

The bottom line: Compromised lung maturity in a live infant is preferable to a deceased infant with healthy lungs.

Timing of delivery

Most experts agree that women with diabetes should be delivered at term—though the definition of “term” ranges from 38 to 42 weeks’ gestation.

At our institution, in addition to the established routine obstetric indications for delivery, 4 additional indications mandate elective delivery for women with diabetes:

• Fetal macrosomia (weight >4,000 g). For large-for-gestational-age fetuses (>90th percentile), induction of labor may be appropriate when fetal weight ranges from 3,800 to 4,000 g and the gestational age is at least 38 weeks. Delivering these fetuses reduces the risk for shoulder dystocia, an ominous complication of diabetes in pregnancy.
  
• History of previous stillbirth—often the result of poorly controlled diabetes—also warrants induction of labor.
  
• Poor compliance or glycemic control. This includes the failure to test blood glucose enough to determine glycemic control; inability or unwillingness to adhere to the diabetic protocol, such as fetal testing; and missed appointments.
  
• Presence of vasculopathy-related hypertension.
  

The road ahead

More pharmacologic alternatives are on the horizon and may include metformin and other oral antidiabetic drugs, insulin glargine and oral insulin, and a technologically improved insulin pump that can interact directly with blood glucose levels.