Gestational diabetes affects up to 18 percent of pregnancies. The increasing prevalence is in part due to more women delaying having children until they are older, as well as to the obesity epidemic.
Women over 40 have a six times greater risk than younger women for gestational diabetes. Other risk factors include a family history of diabetes, elevated BMI (30 or higher), previous delivery of a large baby (greater than 9 pounds) or history of Polycystic Ovarian Syndrome.
Though the exact cause is unknown, gestational diabetes is believed to be related to insulin resistance related to the pregnancy hormones produced by the placenta. Also, the mother's insulin needs become greater in the third trimester. Gestational diabetes usually occurs around the 24-28th week of pregnancy. After delivery of the baby and placenta, blood glucose levels usually go back to normal.
There are inconsistent standards around the world for screening for gestational diabetes, however the Hyperglycemia and Adverse Pregnancy Outcomes study from 1991-2002 has led to tighter recommended screening levels.
It is recommended that all women with any risk factors be screened at first prenatal visit for undiagnosed type 2 diabetes mellitus. If this screening is negative, then it is recommended the woman be screened at 24-28 weeks for gestational diabetes mellitus.
At 24-28 weeks, the screening consists of a one-step approach or a two-step approach. The one-step approach involves checking fasting blood glucose (overnight fast of at least 8 hours) and a one and two-hour blood glucose level after a 75 gram glucose load. Diagnosis is made if any of the following levels are found: equal to or greater than 92mg/dl at fasting, equal to or greater than 180mg/dl at one hour, and equal to or greater than 153mg/dl at two hours.
The two step approach involves a non-fasting, one-hour blood glucose level above 140mg/dl after a 50 gram glucose dose and then the women has to perform a one, two and three hour levels test after a 100 gram glucose dose. Diagnosis is made if two of the following levels are found: equal or greater to 180mg/dl at one hour; equal or greater than 155 at two hours; or equal to or greater than 140mg/dl at three hours.
If diagnosed with gestational diabetes, your doctor will recommend a special meal plan focused on controlling carbohydrate intake. Also, you will be asked to monitor your blood glucose levels while fasting and one to two hours after meals using a home glucose monitor. Sometimes diet and exercise alone is not enough to control the blood glucose levels and diabetes medications may be prescribed for you.
Gestational diabetes can cause some fetal complications including macrosomia (large baby) weighing more than 4,000 grams. This occurs if the mother's blood glucose levels are poorly controlled and the extra glucose from the mother's blood is brought to the fetus, additionally the baby makes extra insulin and stores the extra glucose as fat. This could also lead to the baby having neonatal hypoglycemia (low blood sugar) after delivery. A large baby could increase the need for the mother to have a caesarean section. Other possible fetal complications could include jaundice or respiratory distress.
Some possible short-term effects on the mother include: urinary tract infections, hypertension, pre-eclampsia or difficult labor/delivery. These complications for the mother and baby can be avoided with good prenatal care.
The greatest long term risk for the mother is a 40-60 percent chance of developing type 2 diabetes within five to 10 years post pregnancy. Women can significantly decrease the risk (to 25 percent) by maintaining a healthy weight, eating healthy and exercise. Women are also more likely to have gestational diabetes with any future pregnancy.