Sonographic Findings Associated with Gestational Diabetes in Pregnancies Not Identified by Standard Screening

This study aimed to assess the prevalence of gestational diabetes mellitus (GDM) in women without a prior GDM diagnosis who presented with third-trimester sonographic findings of estimated fetal weight (EFW) >90%, abdominal circumference (AC) >95%, or polyhydramnios.

Between 2018 and 2023, a perinatal diabetes registry tracked pregnant patients >28 weeks of gestation with sonographic findings of EFW >90%, AC >95%, or polyhydramnios (Amniotic Fluid Index [AFI] >25 cm), but no prior GDM diagnosis. These patients underwent a third-trimester 3-hour glucose tolerance test (GTT) or glucose panel. The primary outcome was a new diagnosis of GDM; secondary outcomes included delivery mode, live birth, shoulder dystocia, respiratory distress syndrome (RDS), preeclampsia, neonatal hypoglycemia, and neonatal intensive care unit (NICU) admission.

Of 723 patients, 169 (23.4%) were newly diagnosed with GDM. Among those with specific sonographic findings, GDM was identified in 25.4% (EFW >90%), 24.4% (AC >95%), and 21.2% (polyhydramnios). GDM was diagnosed in 19.5% with one sonographic finding, 25.5% with two, and 26.9% with all three. New third-trimester GDM was significantly associated with increased neonatal hypoglycemia (30.4%; p < 0.001), RDS (10.8%; p = 0.037), and NICU admission (13.4%; p = 0.036).

Up to one in four women with third-trimester findings of EFW >90%, AC >95%, or polyhydramnios-despite a prior negative screen-were newly diagnosed with GDM. These cases were also linked to higher neonatal morbidity. Targeted third-trimester GDM screening in patients with these sonographic markers may help identify at-risk pregnancies and improve perinatal outcomes.

· High rate of missed GDM: Nearly 25% with U.S. findings had late GDM diagnosis.. · Cumulative risk: GDM risk rises with more U.S. findings.. · Neonatal morbidity risk: Later diagnosis linked to higher neonatal risks.. · Clinical implications: Consider later GDM screen if U.S. markers are seen..