Well-controlled type 2 diabetes mellitus in pregnancy showed smaller fetal biometry and neonatal birth weight compared to other glycemic disorders and healthy pregnancies: a comparative cohort study.

Objectives: To compare differences in fetal biometry and obstetric outcomes between healthy pregnant women (group 1) vs. those with prediabetes (group 2), type 2 diabetes mellitus (group 3), and gestational diabetes (group 4) with an adequate metabolic control throughout their pregnancy at a hospital in Northern Mexico. Methods: A retrospective cohort study was conducted, including pregnant women evaluated between 2021 and 2023. We compared the area under the curve (AUC) for biparietal diameter (BPD), abdominal circumference (AC), femur length (FL), and estimated fetal weight (EFW) during the second and third trimesters. Obstetric outcomes were also evaluated. Results: A total of 476 pregnant women were included: 268 in group 1, 88 in group 2, 13 in group 3, and 62 in group 4. Groups 2 and 3 had median HbA1c levels below 6.3% in the three trimesters. No significant differences were observed in the AUC calculated for the EFW, AC, FL, BPD, and AFI. However, women with T2DM had a smaller effect size for AUC of the EFW, FL, and BPD than other groups (Cohen's d = 0.20, d = 0.22, d = 0.26, respectively). The Cohen's d of neonatal birth weight was 0.22 for the prediabetes group, 0.27 for the T2DM group, and 0.12 for the GDM group. No difference was observed in obstetric outcomes. Conclusions: Fetuses of women with T2DM showed smaller AUC values for fetal biometric parameters and neonatal birth weight compared to those of healthy women, even when adequate metabolic control was achieved, in a population with a high prevalence of metabolic disorders.