Maternal Obesity May Spur Fetal Overgrowth

The effects of maternal obesity and gestational diabetes on babies can be observed earlier than previously thought.

New research examined whether “fetal overgrowth” preceded a diagnosis of gestational diabetes and considered potential relationships among overgrowth, gestational diabetes, and maternal obesity overall.

The researchers, whose work was published inDiabetes Care, used ultrasounds to measure fetal abdominal circumference and head circumference at 20 and 28 weeks’ gestation.

Of the more than 4000 pregnant women studied, 171 were diagnosed with gestational diabetes at week 28 of gestation or later.

As early as 20 weeks’ gestation, babies of obese women were more likely to be excessively large around the abdomen, which was determined based on the absolute size of the abdomen and by comparing the size of the abdomen to the size of the head. At the 20-week mark, measurements of babies whose mothers were diagnosed with gestational diabetes were normal, but they were large at the 28-week mark.

The researchers concluded that both gestational diabetes and obesity were linked with accelerated growth of the abdomen between 20 and 28 weeks’ gestation. Women with both gestational diabetes and obesity were almost 5 times more likely to have a baby with large abdominal measurements at 28 weeks.

Study author Gordon C. S. Smith, MD, PhD, DSc, FMedSci, toldContemporary Clinicthat bigger babies temporarily carry risks for complications like stillbirth, obstructed labor, and difficult deliveries.

“In particular, we are concerned about shoulder dystocia, where there is delay following delivery of the baby's head due to excessive size of the body,” Dr. Smith explained. “This can cause trauma (eg, fractures related to manipulations to facilitate delivery) and oxygen deprivation.”

Another long-term issue is that bigger babies of mothers with gestational diabetes are at greater risk for childhood obesity.

Gestational diabetes leads to higher blood sugars in the woman. Once the sugar crosses the placenta, this leads to extra “fuel” for growth, Dr. Smith explained. However, it also means the baby can start producing insulin, which acts as a growth factor, as well.

Dr. Smith suggested that a 2-stage screening of gestational diabetes could be beneficial. Current guidelines recommend screening between 24 and 28 weeks’ gestation, but screening closer to 24 weeks could lead to better outcomes.

However, Dr. Smith pointed out that earlier screening could lead to missed gestational diabetes down the road. He stressed that clinical trials are needed to test implementing screening earlier.

If retail clinicians provide care to pregnant women who are obese, they can provide patient counseling on the risks of gestational diabetes. In doing so, nurse practitioners and physician assistants can recommend that pregnant women avoid eating excessive amounts of simple carbohydrates while controlling portion sizes, consuming lots of fruit and vegetables, and staying active.

If pregnant women are offered a screening test, they should take it between 24 and 28 weeks of pregnancy.

“If they cannot make a 28-week appointment, the test should be done earlier (although not before 24 weeks), rather than later,” Dr. Smith said.