Perinatal Outcomes According to Treatment Targets for Gestational Diabetes: A Multi‐Centre Retrospective Cohort Study

Background Gestational diabetes (GDM) is currently diagnosed in approximately 18% of pregnancies in Australia. GDM may lead to infants being born large for gestational age (LGA), and other complications. There is currently no consensus on optimal treatment targets. Aims This study aims to compare perinatal outcomes in patients with GDM when treated according to tighter or less tight fasting blood glucose level (BGL) targets. Methods Our retrospective cohort study included data from all 12 metropolitan public hospitals providing maternity care in Victoria between January 2020 and December 2022. Women who gave birth to a term singleton infant and who had a diagnosis of GDM were included. Women were grouped according to their delivery hospitals' fasting BGL targets: ‘tighter’ (< 5.0–5.2 mmol/L) or ‘less tight’ (< 5.5–5.6 mmol/L). The primary outcome was LGA and a range of secondary outcomes were compared. Inverse probability treatment weights were calculated based on sociodemographic and socioeconomic factors. We then performed multilevel Poisson regression with delivery hospitals as random intercept. Results There were 25 041 births included, 12 423 (49.6%) in the ‘tighter’ target group, and 12 618 (50.4%) in the ‘less tight’ group. After adjusting for hospital and maternal demographics, there was no difference in LGA births (10.4% in ‘tighter’ vs. 9.5% in ‘less tight’ ( p = 0.85)). More women received insulin treatment in the ‘tighter’ group (53%) compared to ‘less tight’ (35%, p < 0.001). There were no significant differences in secondary outcomes. Conclusion Tighter fasting BGL targets were not associated with improved perinatal outcomes but were associated with an increase in pharmacotherapy.