Do HbA1c levels during pregnancy predict offspring birthweights in women with pregestational diabetes? A retrospective study

Abstract

Background: Pregestational diabetes poses risks of adverse pregnancy outcomes including macrosomia. Haemoglobin A1c (HbA1c) levels provide information on glycaemia over time.

Objectives: The primary aim was to assess whether sequential HbA1c levels predict macrosomia. Secondary aims included gestational age at delivery.

Design: All women in Tygerberg Academic Hospital with pregestational diabetes, who delivered from January 1, 2022 to June 30, 2024 were included. The Ethics Committee of Stellenbosch University granted approval.

Results: Of the 112 patients, 28% had Type 1 diabetes or LADA, collectively designated Group A. 72% of all patients had Type 2 diabetes or MODY, collectively designated Group B. The proportion of macrosomic babies was 26% in Group A, and 24% in Group B. Amongst macrosomic babies, 50% were born preterm in Group A, and 10% in Group B. In Group B, a low positive correlation was observed between the third trimester HbA1c and the birthweight centile (p = 0.03, r = 0.24). Furthermore, the difference between the mid- and third trimester HbA1c values showed that the greater the upward difference, the higher the birthweight centile (Group A: p < 0.01, r = 0.51; Group B p = 0.01, r = 0.28).

Conclusion: An increasing difference between mid- and third trimester HbA1c values correlated positively with higher birthweight centiles.