Background/Aim:
The use of one week of capillary glucose monitoring as a screening tool for late-onset gestational diabetes mellitus (GDM) in women with suspected large for gestational age (LGA) fetuses was evaluated.

Methods:
A retrospective chart analysis was performed on women referred for capillary glucose testing in the third trimester due to fetal ultrasound findings of LGA. Maternal baseline demographics, rates of late-onset GDM diagnosis, management of late-onset GDM and maternal obstetric and neonatal outcomes were collected for women who birthed between January 2023 and December 2025 in a Sydney tertiary teaching hospital.

Results:
45 women were referred for home capillary glucose testing due to LGA. Mean gestational age at time of capillary glucose monitoring was 34 weeks and all women had at least one negative oral glucose tolerance test prior. 11 women were diagnosed with hyperglycaemia consistent with GDM (24%). All of these women were noted to have fasting hyperglycaemia, with three also experiencing post-prandial hyperglycaemia. Five women had hyperglycaemia inadequately responsive to diet control and required medical management with insulin therapy. Mean gestation of birth for the women diagnosed with late-onset GDM was 39 weeks + 0 days with mean birth weight of 3735g compared to 39 weeks +3 days and 3817g in women with LGA but not diagnosed with late-onset GDM. Rates of vaginal birth were lower in women diagnosed with late-onset GDM, however rates of neonatal complications in this group were not increased.

Conclusions
Late onset GDM is diagnosed in a quarter of women referred for capillary glucose testing due to fetal LGA, with fasting hyperglycaemia noted in all positive cases. Larger studies are required to establish whether treatment of late GDM confers clinical benefit.