Suboptimal Nocturnal Glucose Control Is Associated With Large for Gestational Age in Treated Gestational Diabetes Mellitus

Continuous glucose monitoring (CGM) provides far greater detail about fetal exposure to maternal glucose across the 24-h day. Our aim was to examine the role of temporal glucose variation on the development of large for gestational age (LGA) infants in women with treated gestational diabetes mellitus (GDM). We performed a prospective observational study of 162 pregnant women with GDM in specialist multidisciplinary antenatal diabetes clinics. Participants undertook 7-day masked CGM at 30-32 weeks' gestation. Standard summary indices and glycemic variability measures of CGM were calculated. Functional data analysis was applied to determine differences in temporal glucose profiles. LGA was defined as birth weight ≥90th percentile adjusted for infant sex, gestational age, maternal BMI, ethnicity, and parity. Mean glucose was significantly higher in women who delivered an LGA infant (6.2 vs. 5.8 mmol/L, = 0.025, or 111.6 mg/dL vs. 104.4 mg/dL). There were no significant differences in percentage time in, above, or below the target glucose range or in glucose variability measures (all > 0.05). Functional data analysis revealed that the higher mean glucose was driven by a significantly higher glucose for 6 h overnight (0030-0630 h) in mothers of LGA infants (6.0 ± 1.0 mmol/L vs. 5.5 ± 0.8 mmol/L, = 0.005, and 108.0 ± 18.0 mg/dL vs. 99.0 ± 14.4 mg/dL). Mothers of LGA infants run significantly higher glucose overnight compared with mothers without LGA infants. Detecting and addressing nocturnal glucose control may help to further reduce rates of LGA in women with GDM.