Background: Neonatal hypoglycaemia (NH) is a common complication of gestational diabetes mellitus (GDM). Data about the association between antenatal glycaemic control and NH are limited.

Aim: To identify predictors of NH, and particularly the impact of glycaemic management on NH, in GDM pregnancies.

Methods: We conducted a retrospective analysis of GDM women diagnosed according to ADIPS2014 criteria at Bankstown-Lidcombe Hospital (between May 2019 and December 2022). Multiple pregnancies, non-livebirths, and births at other hospitals were excluded. Variables collected included maternal age, gravida/parity, BMI, ethnicity, gestational weight gain according to Institute of Medicine (IOM) targets, gestational age at diagnosis and delivery, mode of delivery, OGTT results, HbA1c, other neonatal complications, and self-monitored blood glucose (SMBG) levels over a one-week period at each patient’s first, second, and last visit to clinic. Women were treated to capillary glucose targets: fasting<5.3mmol/L, 1hr<7.4mmol/L and 2hr<7.0mmol/L. Cases were grouped by the presence or absence of NH (defined as a neonatal BGL <2.6mmol/L). Univariate analyses included independent samples t-tests for continuous variables and Chi-square analyses for categorical variables. Variables significant on univariate analyses (p<0.05) were included in a logistic regression. SPSS version 27 was used for analyses. Crude and adjusted odds ratios were calculated.

Results: There were 810 women with GDM during the study period. NH occurred in 84 infants (10.4%). In over half of these cases, NH was detected on the initial infant capillary glucose check and 93% (n = 78) were detected within three pre-feed glucose checks as prescribed by local protocol in high-risk infants. Rates of NH were similar between diet- and insulin-treated cases. On univariate analysis, a significantly increased risk of NH was seen in women with >30% of SMBG readings above target at the first, second and last visits, in overweight women, and with fasting BGL ≥5.3mmol/L on OGTT. Neonatal factors conferring an increased risk of NH included prematurity, emergency caesarean, LGA, and jaundice. On multivariate analysis, only >30% of SMBG readings above target at the last visit (aOR 2.06, 95%CI 1.01-4.18) and deliveries by emergency caesarean section (aOR 2.10, 95%CI 1.20-3.70) remained significant.

Conclusion: Screening infants of women with GDM using three capillary glucose levels is sufficient to capture most cases of NH. Dysglycaemia toward the end of pregnancy and emergency caesarean birth are associated with a two-fold increase in the risk of neonatal hypoglycaemia. Appropriate screening for NH is essential in these infants.