Using maternal glycosylated haemoglobin as well as glucose tolerance tests identified significantly more mothers with high birth weight in their offspring

Published Date: 01st September 2024

Publication Authors: Green. L, Pankaja. S, Christian. S

Conference Abstract

Background and aims: Gestational diabetes (GDM) is associated with high birth weight neonates, which leads to increased birth injuries in newborns. GDM is classically diagnosed using glucose tolerance test (GTT) during pregnancy, which is cumbersome and inconvenient to a patient. Glycosylated haemoglobin (HbA1c) has been recommended for diagnosing diabetes outside pregnancy, and during the COVID pandemic was applied to pregnant mothers. We aimed to determine the utility of HbA1c in pregnancy outcome by comparing association of maternal HbA1c and birth weight of offspring.
Material(s) and Method(s): The customised birth weight percentile of offspring in Mersey/West Lancashire Teaching Hospitals NHS Trust between 1st May 2019-31st July 2021 in mothers at high risk of gestational diabetes was compared to analysed results HbA1c only, GTT only, or both. An HbA1c >=39 mmol/mol or fasting plasma glucose level >=5.6 mmol/litre, or a 2-hour plasma glucose level >=7.8 mmol/litre in GTT were used to define GDM. Chi-squared was used to calculate odds ratio (OR) using cases where both tests were negative as a reference. It should be noted that many of the high-risk mothers once diagnosed with GDM would have been referred to the diabetes service and so could have made changes to reduce potential birth weight of their baby.
Result(s): Medical records for 1327 women (HbA1c: n=981, GTT: n=1076, both GTT and HbA1c: n=730) with singleton pregnancies were reviewed. The demographic characteristics were similar in these 3 groups, with median age of 30, median body mass index of 31, and 92% white ethnicity. To avoid sample bias, we focused on women who had both HbA1c and GTT results (n=730). As shown in the table, 547 women had HbA1c <39 mmol/mol and negative GTT, with 72 women (13% of 547) had macrosomic neonates. In women with HbA1c >=39 mmol/mol (total n=96), 27 of whom (28%) had macrosomic neonates (OR=2.58;p=0.002), whereas in women with positive GTT for GDM (total n=113), 27 of whom (24%) had macrosomic neonates (OR=2.07;p=0.004). In women with both HbA1c >=39 mmol/mol and positive GTT (n=26), 8 women (31%) had macrosomic neonates (OR=2.9;p=0.011). When GTT and HbA1c were both used, the numbers of identified mothers increased by 70% from 27 (23% of total macrosomia) to 46 (39%).
Conclusion(s): Glycosylated haemoglobin may identify other pregnancies at risk of complications from macrosomic neonates than GTT. Therefore HbA1c could be used to supplement and further stratify high risk women who may require additional fetal growth scans to identify macrosomia in GDM women. If women are identified with fetal macrosomia at growth scans, appropriate intrapartum management could be implemented to reduce maternal and neonatal morbidity arising from unrecognised macrosomia at time of delivery.

Wu, P.; Green, L.; Pankaja, S.; Christian, S.; Et al. (2024). Using maternal glycosylated haemoglobin as well as glucose tolerance tests identified significantly more mothers with high birth weight in their offspring. Diabetologia. 67(Supp 1), pp.S241-S242. [Online]. Available at: https://dx.doi.org/10.1007/s00125-024-06226-0 [Accessed 4 February 2026].