Because gestational diabetes usually develops around the 24th week of pregnancy, a glucose screening test (also called the glucose challenge test) is given between 24 and 28 weeks to measure how well your body handles glucose. In this test, your blood is drawn one hour after drinking a very sweet liquid containing glucose. If that number is 135 or higher, you could have gestational diabetes.
In the U.S., that screening test is followed up with a three-hour glucose tolerance test. This diagnostic test measures your fasting blood sugar — your blood sugar on an empty stomach — as well as your blood sugar one hour after drinking the sweet liquid, then two hours later, and again at three hours. “Two abnormal levels indicate gestational diabetes,” explains Dr. Zork.
If it is not treated, gestational diabetes can cause complications for both mothers and babies. Mothers face the risk of C-section, preeclampsia, or high blood pressure in pregnancy, and developing type 2 diabetes later in life. Babies might weigh too much (which can make moving through the birth canal difficult), experience breathing problems, and have low blood glucose — hypoglycemia — right after birth.