Association between maternal hemoglobin level and the outcome of newborns: a narrative review

Background: Anemia during pregnancy remains a significant public health concern, particularly in developing countries, with implications for maternal and neonatal health. Both low and elevated maternal hemoglobin (mHb) concentrations have been associated with adverse birth outcomes, though findings across studies remain inconsistent. Objective: This literature review aims to evaluate the relationship between maternal hemoglobin levels during pregnancy and neonatal outcomes, including low birth weight (LBW), preterm delivery, small-for-gestational-age (SGA), and perinatal morbidity and mortality. Methods: Relevant studies, including meta-analyses, cohort studies, and systematic reviews, were analyzed to summarize current evidence regarding the impact of maternal anemia and elevated hemoglobin on pregnancy outcomes. Results: Maternal anemia was consistently associated with increased risks of LBW, preterm birth, low Apgar scores, and neonatal morbidity. Meta-analyses reported significantly elevated risks, with severe anemia (Hb <7.0 g/dL) linked to nearly threefold higher odds of LBW. Conversely, elevated mHb levels (>13.0–14.0 g/dL) were also associated with increased risks of SGA and intrauterine growth restriction, likely due to reduced plasma volume expansion and impaired placental perfusion. However, some studies reported no significant association between high mHb levels and adverse neonatal outcomes. Conclusion: Both low and high maternal hemoglobin concentrations pose risks for adverse neonatal outcomes, underscoring the need for routine monitoring and individualized interventions. Further research is warranted to define optimal hemoglobin thresholds and address population-specific factors influencing maternal anemia and hemoconcentration.