Associations of hemoglobin trajectories and time in target hemoglobin range with adverse pregnancy outcomes: a real-world pregnancy records-based study

Objective This study aimed to evaluate associations of hemoglobin trajectories during pregnancy and time spent within clinically recommended hemoglobin ranges (Hb-TITR) with adverse pregnancy outcomes. Methods A retrospective cohort study was conducted using pregnancy records from Shanghai First Maternity and Infant Hospital (from January 2022 to December 2024), involving 7,653 pregnant women with complete serial hemoglobin measurements. Hemoglobin trajectories were categorized as stable, descending, or ascending. Hb-TITR was calculated based on clinically recommended hemoglobin ranges throughout pregnancy. Logistic regression analyses were performed to determine associations with adverse outcomes, adjusting for maternal age, pre-pregnancy BMI, and gestational age. Results Among participants, 85.2% exhibited stable hemoglobin trajectories, 10.4% descending, and 4.4% ascending. Descending trajectory was significantly associated with increased risk of composite adverse outcomes [adjusted odds ratio (OR) 3.92; 95% CI, 3.30–4.66] compared with the stable group. Conversely, ascending trajectory showed no significant risk elevation (OR 1.13; 95% CI, 0.83–1.51). Reduced Hb-TITR (<80%) significantly increased the odds of adverse outcomes (OR 1.35; 95% CI, 1.10–1.65), whereas longer Hb-TITR was protective. Descending trajectories notably increased risks of PROM, cesarean section, postpartum hemorrhage, macrosomia, SGA, and LGA infants. Conclusion Descending hemoglobin trajectories and reduced time spent within recommended hemoglobin ranges during pregnancy were significantly associated with increased risks of adverse maternal and neonatal outcomes, highlighting the importance of monitoring hemoglobin dynamics throughout pregnancy.