Gestational diabetes is a condition in which diabetes is diagnosed during the pregnancy in patients who have no prior history of diabetes. This is one of the most common medical complications occurring in pregnancy. Gestational diabetes may occur in up to 14 percent of all pregnancies and screening of all pregnant patients is routine. The condition results from hormonal changes which normally occur in pregnancy which make the pregnant patient unable to properly metabolize carbohydrates in meals. The potential consequences of gestational diabetes are increased fetal size and weight (macrosomia), increased amniotic fluid volume (polyhydramnios), difficult delivery and increased risk for c-section, possibly metabolic or respiratory problems with the newborn baby, and hypoglycemia in the initial newborn period. It is currently unclear if infants of gestational diabetics are more likely to have diabetes themselves but it is clear that mothers who are gestational diabetics are at markedly increased risk of diabetes later in life (60 to 70 percent risk) and are at increased risk for gestational diabetes in subsequent pregnancies as well.
Some patients are at increased risk for gestational diabetes. The risk factors for gestational diabetes include:
- Women over 30
- Women with body mass index greater than 25
- Women with strong family history of diabetes (first degree relative)
- Women with prior abnormal glucose testing
- Women of ethnic groups with known increased risk (Hispanic, African, Native American, South or East Asian, or Pacific Islands)
Screening and Diagnosis of gestational diabetes
The screening test most commonly used is a 50 gram, 1-hour glucose challenge test which does not need to be done in a fasting state. A screening challenge is considered abnormal if the blood sugar obtained at 1 hour is greater than 130. Test sensitivity is 79 percent and specificity is 87 percent. Some physicians will use a cut off value of 135 and some 140. The ADA ascribes sensitivity of 90 percent and to a cut off of 130 and 80 percent sensitivity to a cut off of 140. Different physicians use different cut off levels often based on the presence or absence of other risk factors. Patients with 1-hour values below 130 are considered normal and no further testing is recommended. Patient with 1-hour values greater than 200 are treated as diabetic, and those patients between 130 and 200 need to take the diagnostic 3-hour test.
The diagnostic test is the 100 gram, 3 hour glucose tolerance test. The test is administered in the morning following an overnight fast. Patients follow an unrestricted diet prior to the test but should ingest at least 150 grams of carbohydrates per day for the three days prior to the test. Failure to do so may result in a false positive test. The diagnosis of gestational diabetes is made if 2 or more values on the test are above the normal threshold.
Treatment of gestational diabetes
Treatment, initially, of women who are diagnosed with gestational diabetes involves both nutritional and dietary consultation. You will be given dietary recommendations as outlined by the American Diabetes Association. This diet is individualized for each patient at the time of the consultation and will regulate the total number of calories as well as the percentage of fat, carbohydrate and protein which should be ingested on a daily basis.
As a general rule, the more active you are the better you will metabolize carbohydrates in your meals. Therefore, you will be instructed to increase you activity especially following meals in order to increase your metabolic rate and better help your body metabolize these sugars. You need to check with your individual physician to discuss the amount and type of exercise you can and should obtain.
Blood Sugar Monitoring
Blood sugar is monitored on a daily basis. You will monitor you blood sugar using a glucometer and record the values for your physician to review. Generally, blood sugar is taken fasting prior to breakfast (goal 70-95) and then 1 (goal less than 140) or 2 (goal less than 120) hours following each meal. Again, there are cut off values for normal and abnormal for each of these times. A consistent pattern of blood sugar elevation which cannot be corrected by dietary changes or increased exercise will then be treated medically. There are no specific criteria which are used to judge these sugars and the degree of abnormality and monitoring is individualized for you.
Medication (oral or injections)
Patients who fail dietary and exercise treatment will need medication to control their blood sugars. The most common medication used today for control of glucose is an oral medication called Glyburide. The timing and dosage of this medication can be altered to fit the individual needs of the patient. This medication works best in those patients who are very compliant with the diet and exercise and usually will not work as well in those whose fasting blood sugars are high. This is safe for the baby and is now the first line of therapy in the treatment of gestational diabetes. Insulin is the other standard form of medical therapy for diabetes and requires daily injection of insulin in varying dosages. Insulin is recommended for those patients who fail oral therapy and for those who are not compliant with diet and who may or cannot exercise.
Goals of Treatment
The overall goal of therapy is to obtain as normal daily blood sugar values as possible throughout a 24 hour period, avoid large babies and difficult deliveries, to minimize risks of diabetes to the mother and baby; thus, optimizing your chances of a normal outcome for the pregnancy.
Recommended Antenatal (Pre-Delivery) Testing
Pregnancies which are complicated by diabetes in any form are at greater risk and fetal monitoring of growth and well being is often indicated. This will be individualized for each patient in terms of the type and frequency of testing. This may include more frequent ultrasounds for fetal weight, growth and amniotic fluid volume, biophysical profile testing, non-stress testing and in some cases assessment of umbilical blood flow velocity (Doppler studies). These tests are done to assess the health and well being of the baby and are done on a weekly or twice weekly basis.
Recommendations for Delivery
Most pregnancies complicated with gestational diabetes will end with a normal vaginal delivery at term. Issues related to induction of labor, c-section for delivery and amniocentesis for fetal lung maturity testing need to be made on an individual basis by your doctors and will vary with each patient.
In summary, pregnancies complicated by gestational diabetes require more care to achieve a good outcome. This is one of the most common pregnancy related medical problems we at the Adventist Maternal Fetal Medicine Center will deal with. Physicians at the MFMC have extensive knowledge and expertise in evaluating and managing these patients and will work closely with you private OB/GYN to achieve a good outcome to the pregnancy.