Diabetes Is a Risk in Pregnancy That Carries Risks Beyond

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Routine Screening

Gestational diabetes, which affects about 4 percent of pregnant women, usually occurs midpregnancy, by the 28th week of gestation. Though its causes are unclear, there are some clues, namely placental hormones that suppress the action of insulin in the mother. This can result in insulin resistance: the mother’s pancreas continues to spew out insulin but her body’s cells fail to use it properly to process blood sugar, causing sugar levels to rise in the mother’s blood.

This extra sugar, though not the mother’s insulin, crosses the placenta and raises the baby’s blood sugar level, giving the baby more energy than it needs to grow normally. The result is macrosomia, a “fat” baby often too big to be born naturally without injury to the baby, mother or both.

The baby’s pancreas, stimulated by sugar from the mother, may produce extra insulin, resulting in low blood sugar at birth and an increased risk of breathing problems. These babies are also more likely to become obese children and diabetic adults.

In addition to an added risk of diabetes later in life, a woman with gestational diabetes can develop high blood pressure during pregnancy and may need a Caesarean section to deliver an overly large baby.

Women are at higher than average risk of gestational diabetes if they are overweight, older than 25, have a strong family history of diabetes, have had gestational diabetes during a prior pregnancy, have previously given birth to a baby weighing nine or more pounds, or have been told they are “prediabetic” with blood sugar levels higher than normal. The risk is greater in African-American, Asian and Hispanic women than in Caucasians.

A pregnant woman is unlikely to know her blood sugar is running high unless she is tested. For those with risk factors, a screening test for blood sugar should be done at the first prenatal visit, Dr. Metzger said.

Women not at high risk for gestational diabetes should be tested between weeks 24 and 28 of pregnancy. In this screening test, now routine in prenatal care, the woman swallows a concentrated solution of glucose, and her blood sugar is measured an hour later.

If the result is abnormal, a fasting test for blood sugar is next. After about 14 hours of no food or drink other than sips of water, the woman is given another dose of glucose, and her blood levels are measured hourly for three hours. If those levels are abnormal on two or three measurements, the woman is said to have gestational diabetes, though some doctors think even one abnormal level is a bad sign.Continued...