Management during Labor and the Puerperium
Diabetic management during labor and delivery is
aimed at maintaining maternal euglycemia to avoid
neonatal hypoglycemia. The hyperinsulinemic fetus of
a diabetic mother, having been exposed to hyperglycemia
throughout the pregnancy, exhibits a brisk insulin
response to a glucose challenge. If maternal glucose
concentrations are increased just before delivery, neonatal
hypoglycemia is likely to develop as the newborn
adapts to being cut off from the placental supply of
glucose. Neonatal hypoglycemia can cause seizures and
other problems and so should be avoided. Therefore, at
our institution, point-of-care capillary glucose concentrations
are checked frequently during labor, with a
goal of 70 –120 mg/dL (3.89 –6.66 mmol/L). Although
maternal glucose concentrations in the range of 60 and
even 50 mg/dL are generally well tolerated, healthy
newborns drop their glucose concentrations approximately
in half during the first few hours of life, so it is
best for maternal glucose to be no lower than 70 mg/dLat delivery. Most women with gestational diabetes will
not become hyperglycemic during labor, because they
are not eating (although they are generally allowed to
drink fluids). We often provide an intravenous infusion
of 5% dextrose to meet the caloric needs of labor.
If maternal glucose concentrations exceed 120 mg/dL a
constant intravenous insulin infusion can be administered
starting at 1 U/h. This is virtually always needed
for gravidas with type 1 diabetes, sometimes needed for
those with type 2 diabetes, and rarely necessary for gestational
diabetes.
Once delivery has occurred, and the fetal–placental
unit is no longer releasing hormones that cause insulin
resistance, maternal glucose metabolism generally
rapidly returns to normal. Because some
women with gestational diabetes actually had undiagnosed
preexisting diabetes before their pregnancy, we
measure a fasting plasma glucose on the morning after
delivery to make sure that no further treatment is
needed at that time.