What is the accuracy of an early third trimester sonogram for identifying LGA infants born to GDM patients diagnosed with the one-step approach?

PURPOSE: The one-step approach for screening of GDM will increase the incidence 2- to 3-fold. These larger cohorts may need to target high-morbidity subsets to be cost-effective. We asked whether ultrasound could stratify the GDM patients with the highest risk for a large for gestational age (LGA) infant.

MATERIALS AND METHODS: A retrospective analysis was performed on 413 GDM patients diagnosed using the one-step approach. Ultrasound data from 28 weeks 0 day to 34 weeks 6 days was studied. The abdominal circumference (AC) and EFW at thresholds between 70 and 95% were examined for their prognostic utility. The primary outcome was an LGA infant.

RESULTS: Both the AC and EFW at all gestational ages were predictive of a LGA infant. The AC and EFW at 28-32 weeks 6 days using a threshold of ≥70% showed the following test characteristics: sensitivity (73 versus 66%), specificity (61 versus 77%), positive predictive value (PPV) (30 versus 40%), and negative predictive value (NPV) (91 versus 91%). The specificity of the EFW was significantly higher than the AC (p < .001).

CONCLUSION: Among GDM patients diagnosed using the one-step approach, an elevated AC and EFW in the early third trimester are predictive of a LGA infant. This is a possible cost-effective way to stratify the one-step GDM pregnancies at highest risk for neonatal morbidity.