Fasting blood glucose as a screening measure for late‐onset gestational diabetes in the third trimester

Abstract Objective To investigate the positive rate of late‐onset gestational diabetes mellitus (GDM) by additional fasting blood glucose (FBG) screening at 32–34 gestational weeks (GW) and analyse the perinatal outcomes of late‐onset GDM after standard treatment. Design An Prospective cohort study. Setting Single centre in China. Population 1130 singleton pregnancies with negative GDM screening in their first and second trimester. Methods Additional FBG testing was performed at 32–34 GW. Pregnancies with FBG ≥5.1 mmol/L were diagnosed as GDM and received standardized treatment. Perinatal outcomes were collected and compared. Main Outcome Measures Diagnosis of late‐onset GDM, obstetric and neonatal outcomes. Results 6.3% (71/1130) of participants had FBG values ≥5.1 mmol/L and were diagnosed with late‐onset GDM. Sixty‐five (91.5%) were treated by dietary therapy and 6 (8.5%) by insulin therapy. The perinatal outcomes of full‐term delivery were compared. The incidence of macrosomia (22.7% vs. 5.1%, adjusted odds ratio (aOR) 5.51, 95% confidence interval (CI) 1.83–16.61, p = 0.002) and NICU transferring (18.3% vs. 10.1%, aOR 1.94, 95% CI 1.01–3.74, p = 0.046) was significantly higher in late‐onset GDM group than that in FBG <5.1 mmol/L group. Elevated FBG was associated with overweight or obesity during pregnancy (54.9% vs. 34.9%, OR 2.27, 95% CI 1.40–3.68, p = 0.001). Conclusions 6.3% of singleton pregnancies with normal GDM screening results in the first and second trimester were found to have late‐onset GDM by additional FBG screening at 32–34 GW, and their risk of macrosomia during a full‐term pregnancy remains significantly higher after standard treatment.