Mild Gestational Diabetes Ups Risk for Women and Their Children

Women with gestational diabetes — which was diagnosed using broader "new" criteria — were five times more likely to develop type 2 diabetes and three times more likely to develop prediabetes in the decade after pregnancy than other pregnant women in a large global observational study.

Children whose mothers had had gestational diabetes were also more likely to be obese, have high body fat, a large waist circumference, and skinfolds at age 11 years. (However, for the combined coprimary outcome of overweight or obese, there was no significant difference between 11 year olds of mothers with versus without gestational diabetes).

These findings are from a follow-up of close to 5000 mothers and offspring from the Hyperglycemia and Adverse Pregnancy Outcome (HAPO) study by William L. Lowe Jr, MD, from Northwestern University, Chicago, Illinois, and colleagues, which was published online September 11 in JAMA.

The researchers diagnosed gestational diabetes using the "new" International Association of Diabetes and Pregnancy Study Groups (IADPSG) criteria (Diabetes Care. 2010;33:676-682) published in 2010 and adopted by the World Health Organization and American Diabetes Association, but not the American College of Obstetricians and Gynecologists, which still advises using the stricter Carpenter-Coustan criteria.

The looser IADPSG criteria for diagnosing gestational diabetes require one abnormal glucose value during an oral glucose tolerance test, whereas the Carpenter-Coustan criteria require two abnormal values.

Milder Gestational Diabetes Is Not Without Risk

"The new criteria are lower and more sensitive and do identify a larger group of women [roughly twice as many]" with gestational diabetes, senior author Boyd E. Metzger, MD, from Northwestern University, told Medscape Medical News.

This study also shows that "unfortunately, a mother's blood sugar level, as identified by mild gestational diabetes, is directly associated with the child's risk of being obese early in puberty," he added.

"From a public health point of view, if a condition is treatable," Metzger continued, "we should identify it as early as we can. The challenge is to have your treatment be as cost-effective as possible."

The first-line treatment for gestational diabetes "is diet and lifestyle, and there have been two clinical trials that showed treating mild gestational diabetes reduces adverse outcomes in the pregnancy" by more than 80% and 90%, without costly medication or ultrasound, he noted.

So "rather than limiting the number" of women with gestational diabetes that are being diagnosed and treated, "we also need to focus a lot on making our treatments more efficient and less costly."

Prediabetes can also be treated by lifestyle changes, he stressed.

"I really think," Metzger summarized, "that mild elevations in blood sugar during pregnancy have important implications for both the mother and child."

Lower Gestational Diabetes Threshold, Impact on Mother and Child

The HAPO study (N Engl J Med. 2008;358:1991-2002) enrolled close to 25,000 pregnant women at 15 sites in nine countries between 2000 and 2006 and found that women who had glucose levels that were high — but lower than levels needed to make a diagnosis of diabetes at that time — had a higher risk of an adverse pregnancy outcome, the researchers explain by way of background.

The women were a mean age of 30 years and of diverse ethnicity: white (47%), Asian (25%), black (16%), Hispanic (10%), and other (2%).

For the current follow-up, the researchers aimed to see if gestational diabetes, diagnosed using the lower threshold criteria issued in 2010, would predict whether mothers would have a greater risk of developing prediabetes or type 2 diabetes and if their children would have greater adiposity during a 10- to 14-year follow-up.

Of more than 15,000 eligible mother-child pairs in the original HAPO study, 9322 pairs were screened at 10 sites, and 4834 children and 4696 mothers took part in the follow-up.

The primary maternal outcome was a composite of type 2 diabetes or prediabetes. The primary outcome for children was being overweight or obese, and secondary outcomes were obesity, body fat percentage, waist circumference, and sum of skinfolds (> 85th percentile for the latter three outcomes).

Based on IADPSG criteria, 14.3% of the women were diagnosed with gestational diabetes. These women tended to be older, had a higher BMI, and were more likely to have a family history of diabetes.

A greater percentage of women with gestational diabetes versus no gestational diabetes developed type 2 diabetes (10.7% vs 1.6%) or prediabetes (41.5% vs 18.4%) during follow-up (P < .001 for both), and these significantly higher risks persisted even after adjustment for multiple variables.

However, when they were 11 years old, a similar number of the children were overweight or obese, regardless of whether or not their mothers had gestational diabetes (39.5% vs 28.6%, respectively; not significant after adjusting for confounders).

The children whose mothers had gestational diabetes, however, were more likely to be obese (19.1%) than the other children (9.9%), and other measures of adiposity were also worse.

Study Not Designed to Pit New Versus Old Gestational Diabetes Criteria

The researchers explain that in the United States gestational diabetes is typically diagnosed in a step-wise way using a 50-g glucose challenge test and then a 3-hour 100-g oral glucose tolerance test.

Then, using Carpenter-Coustan criteria, a woman is diagnosed as having gestational diabetes if she has two of the following abnormal glucose values over 3 hours:

Fasting plasma glucose > 95 mg/dL
1-hour plasma glucose > 180 mg/dL
2-hour plasma glucose > 155 mg/dL
3-hour plasma glucose > 140 mg/dL

In contrast, using the IADPSG criteria a woman is diagnosed as having gestational diabetes if she has one abnormal glucose value using a 2-hour 75-g oral glucose tolerance test based on the same cutoffs.

"This study was not designed to compare women with versus without gestational diabetes defined by the Carpenter-Coustan criteria," the researchers write.

However, more than twice as many mothers with IADPSG-defined gestational diabetes compared with mothers with Carpenter-Coustan–defined gestational diabetes (ie, 240 vs 106) developed a disorder of glucose metabolism, and similarly, about twice as many offspring had poor measures of adiposity.

"The risks for the large group of women meeting the IADPSG-defined criteria for gestational diabetes were substantial and cannot be ignored from a public health perspective."

The research was supported by a grant from the National Center for Advancing Translational Sciences, National Institutes of Health. Metzger has reported no relevant financial relationships. Disclosures for the other authors are listed in the article.

JAMA. Published online in September 11, 2018. Abstract

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