Switching to the new one-step screen for gestational diabetes, recommended by the International Association of the Diabetes and Pregnancy Study Group and endorsed by the World Health Organization, failed to reduce the rates of large-for-gestational-age neonates, macrosomia, neonatal intensive care unit admissions, preterm births, preeclampsia, and shoulder dystocia, according to a new study.
Clinicians in the United States have traditionally screened for gestational diabetes using a two-step test early in gestation in those patients considered high risk, with a second test at 24-28 weeks of gestation for average-risk patients. Values were considered abnormal if they exceeded those recommended by either the Carpenter and Coustan and Fourth International Workshop–Conference Criteria or the values designated by the National Diabetes Group. The American College of Obstetricians and Gynecologists continues to recommend this two-step approach, according to Dr. R. Klara Feldman of the department of ob.gyn., Kaiser Permanente at Baldwin Park, Montebello, Calif., and her associates.
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But based on the results of observational studies, some in the ob.gyn. community thought that expanding the number of women diagnosed and treated early would decrease the number of LGA neonates and related complications. In 2010, the IADPSG and the WHO recommended that instead of the two-step screen, clinicians should perform a hemoglobin A1c test, a random plasma glucose test, or a fasting plasma glucose test at the first prenatal visit to identify undiagnosed pregestational diabetes. For all women not found to have pregestational diabetes, a one-step, 2-hour glucose tolerance test is recommended at 24-28 weeks.
To determine whether switching to the new screening method decreased the number of LGA neonates as hoped, Dr. Feldman and her associates performed a before-after retrospective cohort study comparing the outcomes of 2,972 singleton pregnancies before their hospital and its affiliated clinics switched from the two-step Carpenter-Coustan screen to the one-step IADPSG screen, with 3,094 singleton pregnancies after the change.
The care of patients with gestational diabetes did not change during this period, and the two study groups showed no significant differences in mother’s prenatal weight, mother’s body mass index at initial prenatal visit, the number of office visits during pregnancy, or the percentage of deliveries requiring labor induction.
The rate of diagnosed gestational diabetes increased as expected after the new screen was implemented, from 17% to 27%. However, the primary outcome measure – the percentage of LGA neonates – did not decrease significantly. That rate was 10% in the “before” group and 9% in the “after” group. Similarly, rates of macrosomia, NICU admission, preterm birth, preeclampsia, and shoulder dystocia remained unchanged after implementation of the new screening approach (Obstet Gynecol. 2016;127:10-7. doi: 10.1097/AOG.0000000000001132).
“The cutoffs chosen by the IADPSG may be too low and thus result in too many patients being treated as having gestational diabetes,” they added. “Different cutoff values need to be evaluated, and more attention needs to be focused on controlling prepregnancy BMI.”
The Kaiser Permanente Regional Research Committee supported the study. Dr. Feldman and her associates reported having no relevant financial disclosures.