Pregnancy Outcomes Among Women with Treated Iron Deficiency Anemia: A Retrospective Cohort Study

Abstract

Background and Objectives: Iron deficiency anemia (IDA) is the most common cause of anemia in pregnant women and can adversely affect both maternal and fetal health. This study aimed to compare pregnancy outcomes between women with and without IDA in Northern Thailand, a region with a high prevalence of anemia. Methods: A retrospective cohort study was conducted on all singleton pregnancies attending antenatal care (ANC) and/or delivering at Maharaj Nakorn Chiang Mai Hospital between 2003 and 2024. The study group consisted of women diagnosed with IDA in the first half of pregnancy, while the control group comprised women with low-risk pregnancies during the same study period. Results: Of the 38,979 pregnancies, after applying exclusion criteria, 634 pregnancies (2.2%) with laboratory-confirmed IDA and 28,132 controls remained available for analysis. Women with IDA had significantly higher parity, lower socioeconomic status, and lower hemoglobin levels throughout pregnancy. Multivariate regression analysis revealed that IDA was significantly associated with increased risks of preterm birth (adjusted odds ratio; aOR 1.04; 95% CI: 1.01–1.07), fetal growth restriction (FGR) (aOR 1.02; 95% CI: 1.00–1.04), and low birth weight (aOR 1.05; 95% CI: 1.03–1.08). Conclusions: IDA, even with treatment, may still slightly increase the risk of adverse pregnancy outcomes, particularly preterm birth, fetal growth restriction, and low birth weight. The residual risk likely reflects incomplete correction of anemia. Optimizing management requires strict compliance, judicious use of parenteral iron, and attention to coexisting nutritional deficiencies, underscoring the need for closer monitoring and improved care strategies.