Pregnancy is characterized by insulin resistance and and hyperinsulinemia, thus it may predispose some women to develop diabetes. The resistance stems from placental secretion of diabetogenic hormones including growth hormone, placental lactogen, corticotrophin releasing hormone and progesterone, as well as increased maternal adipose deposition, decreased exercise, and increased caloric intake. These metabolic changes ensure that the fetus has an ample supply of fuel and nutrients at all times. Gestational diabetes occurs when pancreatic function is not sufficient to overcome the insulin resistance created by changes in the diabetogenic hormones during pregnancy.
Universal screening for Gestational Diabetes occurs between 24 and 28 weeks of pregnancy because this is the time when the diabetogenic hormones peak.
The goal is to maintain normoglycemia to ensure a good outcome for both mother and baby. The patient with gestational diabetes is required to monitor blood glucose levels throughout the day via fingerstick. The aim is to maintain fasting blood sugars between 60 and 95 mg/dL and 2 hr postprandial blood sugars < 120 mg/dL.
Upon diagnosis, patients with gestational diabetes should receive nutritional counseling from a registered dietician and be placed on an appropriate diet. The goals of nutritional therapy are to:
Once initiated on the diet, the patients should be seen weekly and the blood sugars closely watched to assess if pharmacologic therapy is necessary.
If normoglycemia cannot be maintained by special diet, anti-hyperglycemic agents should be initiated. The two options for medical therapy in pregnancy are insulin or oral anti-hyperglycemic agents : glyburide or metformin, which may be a reasonable alternative for women that fail diet therapy or refuse to take, or are unable to comply with insulin. As with insulin therapy, glyburide and metformin must be carefully balanced with snacks to prevent maternal hypoglycemia.
Women with gestational diabetes are placed on insulin therapy when target glucose levels are not achieved despite dietary and sometimes oral anti-hyperglycemic agents. An insulin regimen is calculated, often consisting of a combination of short acting plus intermediate or long acting insulin and adjusted as necessary to maintain normoglycemia. Titration of insulin dose to blood glucose levels is based upon frequent self-monitoring. At least four glucose measurements are required daily and are needed to optimize therapy and ensure a smooth increase as requirements increase with pregnancy progression.
Although there are no rules, in general the patient with diabetes in pregnancy will receive at least one ultrasound in the third trimester to monitor the fetal growth. This is helpful in ascertaining which patients may benefit from scheduled cesarean section in the fetus is measuring > 4500 g or to see who may benefit from induction of labor before the fetus grows too large.
It is also common practice to initiate fetal testing in the third trimester to ensure fetal wellbeing. The test that is utilized varies by institution and practice and may be either weekly nonstress tests or biophysical profiles. The timing for initiation of testing also varies but generally begins at approximately 32 weeks gestation.
Maternal hyperglycemia should be avoided during labor to reduce the risk of fetal acidosis and neonatal hypoglycemia. The risk of adverse neonatal metabolic outcomes is related to both antepartum and intrapartum maternal hyperglycemia and appears to increase with degree of maternal hyperglycemia. Insulin requirements usually decrease during labor, as uterine contractions require energy and caloric intake is typically reduced. Women with gestational diabetes who were normoglycemic without use of insulin or oral hyperglycemic drugs during pregnancy rarely require insulin during labor and delivery. Women with gestational diabetes who used insulin or oral antihyperglycemic drugs to maintain normoglycemia may need an insulin infusion during labor and delivery. We generally check blood glucose levels every 1-2 hours during active labor in these women and will begin an insulin infusion if necessary. It is generally best to withhold long-acting insulin in favor of using an insulin infusion as needed, in women in labor.
Women with gestational diabetes are able to resume a regular diet postpartum as the hyperglycemic effects of the placental hormones dissipate rapidly. It is at the practitioners discretion if blood glucose testing can be stopped or should be continued for up to 48hrs after delivery.
All patients with gestational diabetes should do the 75 gram oral glucose tolerance test to evaluate for Type II diabetes.
- Postpartum depression is increased amongst women with gestational diabetes
- Gestational Diabetes in future pregnancies is at an increased risk
- Type II Diabetes risk is increased
Written by Dr Carla Ming Reese, Obstetrician/Gynaecologist