Symptoms
Gestational diabetes is a glucose intolerance that is first discovered during pregnancy and is common, occurring in approximately 1-14% of all pregnancies. Typical symptoms of diabetes mellitus such as thirst, frequent urination, and fatigue may occur, but are considered rare. Nonspecific complaints such as increased susceptibility to urinary tract infections may indicate gestational diabetes.
Causes
Pregnancy naturally presents with a diabetogenic state. Beginning in the 2nd trimester, insulin resistance increases and intensifies throughout the remaining months of pregnancy. The main cause is thought to be the increased secretion of hormones such as estrogens, progestins, cortisol, placental lactogen, prolactin, and growth hormone. Among other things, these hormones ensure that adequate glucose is available to the fetus. Women with gestational diabetes have increased insulin resistance and the compensatory secretion of insulin from the pancreas is not sufficient to adequately lower blood glucose. In the fetus, the increased supply of glucose leads to increased insulin production, increased uptake of glucose and nutrients into cells, and thus ultimately increased growth.
Complications
The main complication is fetal weight gain and increased birth weight, which increases the risk for cesarean section and birth complications (eg, shoulder dystocia, asphyxia). Due to sugar deprivation, newborns may develop hypoglycemia. Other fetal complications include hyperbilirubinemia (jaundice), hypocalcemia, hypomagnesemia, and polycythemia (many red cells in the blood). The children have an increased risk of later becoming overweight and developing diabetes themselves. Possible complications for the mother include: Preeclampsia (hypertension, oedema, proteinuria), a more difficult delivery, and the development of diabetes.
Risk factors
An important risk factor is maternal overweight or obesity. Others include gestational diabetes, a history of high birth weight infant or miscarriage, glucose intolerance, glucosuria, and parents or siblings with type 2 diabetes mellitus (heredity). Some ethnic groups and women older than 24 years are also at higher risk.
Diagnosis
Diagnosis and screening vary from country to country. The Swiss Society of Endocrinology and Diabetology recommends that an oral glucose tolerance test be performed in all women between 24 and 28 weeks of gestation (Lehmann et al, 2009). In this test, 75 g of glucose is administered orally to the fasting woman and blood glucose is measured fasting, after one hour and after two hours. An excessively high blood glucose value indicates gestational diabetes. Although young women under 24 years of age with no risk factors are at low risk, many countries recommend testing all women for simplicity. High-risk women should additionally be tested earlier, starting at 12 weeks. The details of screening and diagnosis can be found in Lehmann et al. (2009). In practice, fasting blood glucose determination is often performed.
Nonpharmacologic treatment
Treatment is aimed at reducing blood glucose levels and the risk of increased birth weight and complications. Often, dietary changes (nutritional counseling) and increased physical activity (eg, swimming, stair climbing, walking) are sufficient for this purpose. Patients are given a blood glucose meter with which they can independently measure and monitor blood glucose levels several times a day. They are monitored by a physician during and after pregnancy.
Drug treatment
If nonpharmacologic measures do not achieve the goal, insulins are the drug therapy of choice. They do not cross the placental barrier. Whether the use of certain oral antidiabetic drugs is also safe and appropriate is being discussed and scientifically investigated (e.g., metformin, glibenclamide, or acarbose). Their use would be desirable because they are taken as tablets and do not have to be injected under the skin like insulins. For example, the sulfonylurea glibenclamide is not placenta-compatible according to scientific studies and should not reach the fetus.