Adverse pregnancy outcomes increase with gestational diabetes, maternal obesity

Gestational diabetes and maternal obesity, alone and together, increase the risk of adverse pregnancy outcomes, according to research published in Diabetes Care.

The combination of gestational diabetes and obesity has a greater impact than either one alone, according to the study.

Researchers at Case Western Reserve University at MetroHealth Medical Center in Cleveland analyzed data on more than 23,000 women from nine countries. The women took a 75 gram oral glucose tolerance test between 24 and 32 weeks gestation.

For those women with gestational diabetes alone, the odds ratio for having a newborn baby weighing in the 90th percentile or higher was 2.19 compared to those without gestational diabetes. With maternal obesity by itself, the odds ratio was 1.73.

For both maternal gestational diabetes and obesity, the odds ratio for birth weight greater than 90th percentile was 3.62 compared to mothers without both conditions.

The odds for birth weight were progressively greater with both higher oral glucose tolerance test results and higher maternal body mass index.

Similarly, the odds were significantly higher for having a primary cesarean delivery, preeclampsia, and cord C-peptide greater than 90th percentile for the obese and diabetic cohort.

Clinicians diagnosed 13.7 percent with obesity and 16.1 percent with gestational diabetes. The remaining 64.2 percent had normal glucose and were normal or under weight.

The study defines obesity as body mass index of 33 or higher. The mean maternal body mass index was 27.7.

Adverse pregnancy outcomes include birth weight, newborn percent body fat, cord C-peptide greater than 90th percentiles, primary cesarean delivery, preeclampsia, and shoulder dystocia and birth injury.

Gestational diabetes
Many women develop gestational diabetes during pregnancy, typically around the 24th week. Gestational diabetes affects 18 percent of pregnancies, according to the American Diabetes Association.

While the exact mechanism of gestational diabetes is unknown, scientists suspect that the hormones from the placenta cause insulin resistance in the mother. This may cause the mother to need up to three times as much insulin to make and use all the insulin she needs for pregnancy.

Still, glucose builds up in the blood to dangerous levels, causing hyperglycemia. The extra blood glucose can give the baby high blood glucose levels, causing the baby to gain excess fat. Larger babies are at risk of shoulder damage during birth.

Babies of diabetic pregnancies make extra insulin and are at higher risk for breathing problems at birth. Babies with excess insulin also are at higher risk for childhood obesity and adult type 2 diabetes, according to the American Diabetes Association.

Sources: Diabetes Care, Physicians Briefing, American Diabetes Association