Article Impact Level: HIGH Data Quality: STRONG Summary of Annals of Internal Medicine https://doi.org/10.7326/ANNALS-25-02586 Dr. Leta Shams et al.
Points
- A retrospective cohort study of over one million births identified a U shaped relationship where both low and high maternal hemoglobin levels increased the risk of severe neonatal complications.
- Compared to a baseline of one hundred twenty five grams per liter the risk for neonatal morbidity rose by seventeen percent when maternal hemoglobin dropped to ninety grams per liter.
- Maternal erythrocytosis also posed significant risks as hemoglobin concentrations of one hundred fifty grams per liter were associated with a twenty percent increase in adjusted relative risk for neonatal mortality.
- The findings demonstrate that maternal anemia and relative erythrocytosis are significant predictors of unfavorable perinatal outcomes even within high income settings with robust access to traditional prenatal medical care.
- Researchers recommend that future clinical trials focus on identifying the optimal hemoglobin thresholds for initiating iron therapy to ensure effective correction and improved safety for both mothers and infants.
Summary
This population-based, retrospective cohort study evaluated the association between early pregnancy hemoglobin concentration and severe neonatal morbidity and mortality (SNM-M) within a high-income setting. Utilizing a massive dataset of 1,100,341 singleton births from women aged 18 to 50 years between 2007 and 2023, the researchers analyzed hemoglobin levels measured specifically between 2 and 12 weeks of gestation. The primary objective was to determine if deviations from standard hemoglobin levels correlate with unfavorable perinatal outcomes in resource-rich environments.
The analysis revealed a distinct U-shaped relationship between maternal hemoglobin concentration and neonatal risk. Using a baseline hemoglobin of 125 g/L (associated with a 6.7% SNM-M rate) as a reference, the adjusted relative risk (aRR) for SNM-M rose significantly at both physiological extremes. For maternal anemia, the aRR was 1.08 at 105 g/L and increased to 1.17 at 90 g/L. Conversely, relative erythrocytosis also demonstrated increased risk, with an aRR of 1.05 at 135 g/L and 1.20 at 150 g/L, suggesting that high hemoglobin concentrations are as clinically relevant as low levels.
These findings confirm that both maternal anemia and relative erythrocytosis in early pregnancy are independent risk factors for severe neonatal complications. While anemia affects up to 50% of pregnancies globally, these data underscore the need for precise clinical thresholds in high-resource settings. The researchers conclude that future prospective trials are necessary to evaluate the optimal timing for iron therapy and to determine the specific hemoglobin correction targets required to minimize neonatal morbidity and mortality
Link to the article: https://www.acpjournals.org/doi/10.7326/ANNALS-25-02586
References
Shams, I., Tang, G. H., Wang, X., Walker, M., Baxter, N. N., Gomes, T., Ray, J. G., & Sholzberg, M. (2026). Hemoglobin concentration in early pregnancy and severe neonatal morbidity and mortality: Population-based cohort study. Annals of Internal Medicine, ANNALS-25-02586. https://doi.org/10.7326/ANNALS-25-02586
