Gestational Diabetes Screening Based on Risk Misses Too Many

Miriam E. Tucker

November 15, 2012

Selective screening of pregnant women for gestational diabetes by risk factors misses about a third of women who have the condition and who are at increased risk for adverse pregnancy outcomes, a large retrospective analysis shows.

Findings from a database analysis of 18,775 women delivered at a French hospital between January 2002 and December 2010 were published online November 12 in Diabetes Care by Emmanuel Cosson, MD, PhD, from the Centre de Recherche en Nutrition Humaine d’Ile-de-France, Department of Endocrinology-Diabetology-Nutrition, Jean Verdier Hospital, Assistance Publique-Hôpitaux de Paris, Sorbonne Paris Cité, and the Unité de Recherche Epidémiologique Nutritionnelle, Bobigny, France, and colleagues.

"[T]he selective screening of GDM is appealing, as it reduces the burden of unnecessary screening tests if this screening selects the women who have the highest risk of GDM-related complications. We showed, however, that in our population, such a strategy would lead to missing approximately one-third of the women with GDM," the authors write. "Furthermore," they add, "despite appropriate treatment, women with GDM had a worse prognosis than women without GDM, even if they were free of risk factors. Therefore, universal screening appears to be beneficial."

Of a total 20,653 women who delivered at the hospital during the study period, the study population of 18,775 women included those who did not have preexisting diabetes and for whom the status was known for all of the GDM risk factors: family history of diabetes; prepregnancy body mass index (BMI) of 25 kg/m2 or higher; age 35 years or older; previous pregnancy with GDM, preeclampsia, or malformation; current pregnancy with hypertension; or previous pregnancy with macrosomia.

Screening for women with a history of GDM or 2 or more other risk factors was done at 15 weeks' gestation. The rest of the women were screened between 24 and 28 weeks' gestation. A 1-step 75-g oral glucose tolerance test was used for both screening and diagnosis for all of the women. The diagnosis of GDM was made with fasting plasma glucose of 5.3 mmol/L (95.5 mg/dL) or higher and/or a 2-hour glucose value of 7.8 mmol/L (140.5 mg/dL) or higher.

The women were a multiethnic population with a mean age of 29.7 (±5.8) years and a mean prepregnancy BMI of 24.1 (±4.9) kg/m2. Gestational diabetes was diagnosed in 2710 (14.4%) of the women, and total of 10,975 women (58.5%) had at least a single GDM risk factor. Although the prevalence of GDM remained unchanged during the study period, the prevalence of risk factors rose, with the proportion overweight increasing the most, going from 30.8% in 2002 to 37.6% in 2010 (P < .0001).

The presence of at least a single risk factor significantly predicted the development of GDM, with an odds ratio of 1.4 (95% confidence interval, 1.3 - 1.5), and the prevalence of GDM rose as the number of risk factors increased. However, the sensitivity of the presence of at least a single risk factor for predicting GDM was only 65.3%, leaving a total 940 women (34.7%) who would have been missed by screening only those with risk factors.

The specificity of 1 or more risk factors was 42.7%; the positive and negative predictive values were 16.1% and 87.9%, respectively, Dr. Cosson and colleagues report.

A total of 11.2% of all pregnancies in the study cohort experienced at least a single GDM-associated adverse outcome including preeclampsia, large for gestational age, shoulder dystocia, caesarean delivery, and large for gestational age–related caesarean delivery. Both the presence of GDM and the presence of 1 or more risk factors significantly increased the overall risk for these outcomes (P < .0001).

Among the women diagnosed with GDM, the proportions experiencing adverse outcomes were 18.2% for those with risk factors and 16.7% for those without. Among women without GDM, adverse outcomes occurred in 11.1% with GDM risk factors and 8.8% without.

"There was no interaction between GDM effect and risk factor effect. The higher the number of risk factors, the higher the incidence of GDM-related events," the authors write.

According to an international panel, new GDM diagnostic criteria that they issued in 2010 to lower the threshold for diagnosis are currently under debate. As stated in an article published in Diabetes Care, "[the] decision to perform blood testing for evaluation of glycemia on all pregnant women or only on women with characteristics indicating a high risk for diabetes is to be made on the basis of the background frequency of abnormal glucose metabolism in the population and on local circumstances" (Diabetes Care. 2010;33:676-682).

Parts of this study were presented at the 48th Annual Meeting of the European Association for the Study of Diabetes. The authors have disclosed no relevant financial relationships.

Diabetes Care. Published online November 12, 2012. Abstract