Early screening and diagnosis of gestational diabetes mellitus (GDM) and its impact on perinatal outcomes

Aims: To compare the maternal and neonatal outcomes following early diagnosis compared with routine diagnosis of gestational diabetes (GDM). Methods: In this observational study, 3494 women were categorised by weeks of gestation at GDM diagnosis: early GDM (<= 20 weeks) and routine GDM (>20 weeks). The early GDM group was further divided by treatment commencement as immediate (<12 weeks) and delayed (12-20 weeks) and by diagnostic fasting blood glucose as higher-FBG (5.3-6.0 mmol/L) and lower-FBG group (FBG 5.1-5.2 mmol/L). Primary outcomes were large for gestational age (LGA) and small for gestational age (SGA). Generalized linear models used to calculate risk ratios and adjusted for confounding. Results: Risk ratios (RR) for LGA and SGA were similar for early versus routine diagnosis, and immediate versus delayed treatment. The higher-FBG immediate treatment group had a lower risk of newborn respiratory distress (RR 0.52, 95 %CI 0.34, 0.81) and emergency caesarean (RR 0.55, 95 %CI 0.34, 0.88) compared to the higher-FBG delayed treatment group. Among the lower-FBG group, no such benefits were seen. Conclusions: Fasting glucose levels modified the effects of early treatment of GDM where a higher-FBG with immediate treatment appears to reduce perinatal complications, but treating women with lower-FBG early has no benefits.