SUN-537 Determinants of fetal growth pattern and baby birthweight in a high-risk cohort of women with GDM of Southeast Asian origin

Abstract Disclosure: L.S. Law: None. A.E. Teo: None. D. Lim: None. L. Tan: None. G. Tan: None. T. Yew: None. C. Khoo: None. P. Eng: None. Objective: Gestational diabetes mellitus (GDM) increases neonatal birthweight and the risk of obstetric and neonatal complications. Despite maternal glucose normalization, the risk of elevated neonatal birthweight persists. This study examines maternal factors influencing fetal growth and birthweight in high-risk GDM pregnancies. Methods: This retrospective study analyzed 561 women with singleton pregnancies complicated by GDM, diagnosed at 24-28 weeks via a 75g oral glucose tolerance test (OGTT) per WHO criteria. High-risk GDM was defined as diabetic-range glucose levels on OGTT, diagnosis before 24 weeks, or insulin requirements exceeding 20 units during pregnancy. Fetal growth was assessed via ultrasound at 30-32 and 34-36 weeks. Maternal clinical data, OGTT results, and HbA1c levels were collected. Univariate and multiple regression analyses, adjusted for gestation and parity, were performed to evaluate maternal factors influencing fetal growth and birthweight. Results: Complete data were available for 392 of the 561 women. Pre-pregnancy maternal weight significantly predicted estimated fetal weight (EFW) and abdominal circumference (AC) at both 30-32 weeks (EFW: β = 0.16, p <0.001; AC: β = 0.18, p <0.001) and 34-36 weeks (EFW: β = 0.25, p <0.001; AC: β = 0.22, p <0.001). Higher EFW and AC at 30-32 weeks (EFW: β = 0.51, p <0.001; AC: β = 0.52, p <0.001) and 34-36 weeks (EFW: β = 0.69, p <0.001; AC: β = 0.70, p <0.001) were associated with higher birthweight. OGTT glycemic thresholds (fasting, 1-hour, 2-hour) did not predict EFW or AC, but HbA1c at 24-28 weeks correlated with birthweight (β = 0.11, p = 0.02) without influencing ultrasound parameters. Indian women had the lowest birthweight (β = -0.13, p = 0.004). Indian babies also had a lower AC at 34-36 weeks (β = -0.14, p = 0.021) but not at 30-32 weeks (β = -0.11, p = 0.052). Ethnicity did not influence EFW at either time point. Conclusion: Pre-pregnancy maternal weight significantly predicted fetal growth and birthweight, while HbA1c at 24-28 weeks predicted birthweight but not fetal growth. These findings suggest early fetal growth may be intrinsic and less influenced by maternal glycemia. Ethnicity influenced AC in the third trimester and birthweight, with Indian women having smaller babies. Further research is needed to assess glycemia’s impact on fetal growth and birth outcomes in a multiethnic cohort. Presentation: Sunday, July 13, 2025