Delayed diagnosis of gestational diabetes mellitus and perinatal outcomes in women with large for gestational age fetuses during the third trimester

OBJECTIVE: We evaluated the incidence of newly diagnosed gestational diabetes mellitus (GDM) during the 3rd trimester in women with suspected large for gestational age (LGA) fetuses on ultrasound and assessed their perinatal outcomes. METHODS: A retrospective cohort study was performed. Singleton pregnant women with suspected LGA on the 3rd trimester ultrasound and whose results of GDM screening at midpregnancy had been normal were enrolled. All participants were retested with 100-g oral glucose tolerance test (OGTT) within 2 days after diagnosis of LGA. We compared perinatal outcomes between the newly diagnosed with GDM group and the non-GDM group. RESULTS: Among 169 pregnant women, 13% (23/169) were newly diagnosed with GDM. The women in the GDM group had a higher HbA1c level at diagnosis (5.8 vs. 5.3, P<0.01) and earlier gestational age at delivery (38.0 vs 38.9 weeks of gestation, P=0.003) than those in the non-GDM group. The rate of cesarean delivery (CD) was significantly higher in the GDM group than that in the non-GDM group (73.9%, vs. 49.3%, P=0.028) with similar proportions for the indications of CD except CD on maternal request (CDMR). The CDMR rate was higher in the GDM group than nonGDM group (41.2% vs. 23.6%) but it did not reach statistical significance. There were no significant differences in the obstetrical and neonatal complications between the two groups. CONCLUSION: Among pregnant women with suspected LGA, 13% were newly diagnosed with GDM in late pregnancy. Nonetheless, there were no differences in the perinatal outcomes between women with newly diagnosed GDM and those without GDM. However, concerns over shoulder dystocia appear to increase CD rates in the GDM group.