Mothers' Gestational Diabetes Foretells Kids' Obesity

OAKLAND, Calif., Aug. 28 -- Untreated gestational diabetes nearly doubles the risk that offspring will be obese by kindergarten age, but treatment of maternal hyperglycemia can prevent it, said investigators here.

A retrospective review of records on more than 9,000 mother-child pairs showed that childhood obesity risk rose with the degree of the mother's hyperglycemia during pregnancy, reported Teresa Hillier, M.D., M.S., of the Kaiser Permanente Center for Child Health Research, and colleagues.

The investigators also found, however, that prompt treatment of gestational diabetes reduced the risk that children would become obese compared with the offspring of untreated women, they reported in the September issue of Diabetes Care.

"My advice to pregnant women is three-fold," Dr. Hillier said. "Discuss gestational diabetes screening with your doctor, usually between weeks 24 and 28 of pregnancy; if you have gestational diabetes, work with your physician to treat it, and stick with the treatment during your pregnancy. It's the best thing you can do to reduce your child's risk of obesity."

The authors reviewed records on 9,439 mother-child pairs from Kaiser Permanente facilities in Hawaii and the Pacific northwest. In both regions, universal screening for gestational diabetes was performed with a 50 g oral glucose challenge test.

Women who tested positive on the screen were then tested with a three-hour, 100 g oral glucose tolerance test, with gestational diabetes diagnosed according to National Diabetes Data Group and Carpenter and Coustan criteria.

The National Diabetes Data Group criteria require the following glucose levels on at least two of four readings on the oral glucose tolerance test:

• Fasting: at least 5.8 mmol/L
• One hour: at least 10.5 mmol/L
• Two hours: at least 9.2 mmol/L
• Three hours: at least 8.0 mmol/L.

The Carpenter and Croustan criteria use lower cutoffs to establish the diagnosis:

• Fasting: at least 5.3 mmol/L
• One hour: at least 10 mmol/L
• Two hours: at least 8.6 mmol/L
• Three hours: at least 7.8 mmol/L

"Relevant to this analysis, during 1995-2000, Kaiser Permanente used the NDDG criteria to diagnose and treat gestational diabetes mellitus, allowing us to also assess potential differences in outcomes with treatment," the investigators wrote. "Therefore, those meeting the NDDG criteria were likely to be treated with diet or diet/insulin, but those meeting only the Carpenter and Coustan criteria were likely to not be treated."

They used the measured weight of the children at five to seven years to calculate sex-specific weight-for-age percentiles, using U.S. norms (1963-1994 standard), and then classified them by maternal positive glucose challenge test (one hour values of 7.8 mmol/l or greater) and OGTT results (one or two or more of the four time points abnormal).

They found that there was a positive trend for increasing childhood obesity at five to seven years which paralleled the range of increasing maternal glucose screening values, and was significant for the 85^th and 95^th maternal glucose percentiles vs. the lowest percentile.

In addition, when they adjusted from for potential confounding factors, including maternal weight gain and age, parity, ethnicity, and birth weight.

"Importantly, the increased risk of childhood obesity with maternal gestational diabetes mellitus by NDDG criteria (which was treated) was not significant after multivariate adjustment, whereas the risk of all other levels of hyperglycemia based on > one abnormal oral glucose tolerance test values remained significant," the investigators wrote.

Treatment of gestational diabetes reduced the future obesity risk of children to a level comparable to that of children of mothers with normoglycemia throughout pregnancy, the authors found.

They proposed that one or more episodes of maternal hyperglycemia may result in a "metabolic imprinting" of the child in utero, and that maternal glucose abnormalities during pregnancy, particularly fasting hyperglycemia, are predictive of future obesity risk in children. They also called for further research to determine whether gestational diabetes and its treatment might be a modifiable risk factor for childhood obesity.

The authors noted that their study was limited to only those children who remained in the HMO through weight measures at five to seven years, although changes in membership were likely to be random. They also noted that they did not have data in maternal weight prior to pregnancy, and that their identification of women with diabetes mellitus was based on a single gestational diabetes screening time point.