First-Trimester Complete Blood Count as a Predictor of Gestational Diabetes Mellitus: A Multi-center Primary Health Care Study.

Background Gestational diabetes mellitus (GDM) is a common pregnancy complication linked to significant maternal and neonatal risks, such as fetal risk of large for gestational age (LGA) and polyhydramnios. This study aimed to evaluate the predictive value of first-trimester complete blood count (CBC) parameters - particularly neutrophil count - for the development of GDM among women attending National Guard primary care centers in Jeddah, Saudi Arabia. Methods A retrospective cohort study was conducted using records from January 2023 to January 2024. Pregnant women aged 18-45 years who completed first-trimester laboratory testing and underwent GDM screening at 24-28 weeks were included. Women with pre-existing diabetes, chronic illnesses, or signs of ongoing infections were excluded. Clinical, laboratory, and pregnancy outcome data were analyzed using IBM SPSS Statistics for Windows, Version 29 (released 2022; IBM Corp., Armonk, NY, USA), employing t-tests, chi-square tests, and binary logistic regression to identify significant predictors. Results Among 399 women, 25.6% developed GDM. Significant predictors included older maternal age, higher body mass index (BMI), excessive gestational weight gain, and a history of previous GDM (p < 0.001). Laboratory findings showed elevated fasting glucose and red blood cell (RBC) counts in the GDM group, while neutrophil count and neutrophil-to-lymphocyte ratio (NLR) were not statistically significant predictors. Logistic regression confirmed that the one-hour oral glucose tolerance test (OGTT) value, total weight gain, and previous GDM history were independent predictors, with OGTT showing the strongest association (OR = 3.878, p < 0.001). Conclusion Traditional risk factors, including maternal age, BMI, weight gain, and GDM history, remain crucial for GDM prediction. First-trimester neutrophil counts did not show predictive value, suggesting limited utility as early inflammatory markers.