Iron stores accrued in utero are critical for fetal and infant neurodevelopment. Low neonatal hemoglobin (Hb) may indicate inadequate iron capture and storage. Prior studies differ on whether and under what conditions maternal anemia predicts neonatal Hb; whether sex differences are present is unknown. Maternal and neonatal Hb and sociodemographic and health characteristics were abstracted from electronic medical records for biorepository participants at a tertiary academic medical center. Maternal anemia was defined as Hb < 11 g/dL in trimesters T1 and T3 and Hb < 10.5 g/dL in T2. Adjusted linear regression models were used to estimate associations of maternal anemia with neonatal Hb. Sex differences were evaluated with product terms and stratification. In 228 participants with maternal Hb measured, the prevalence of prenatal (pre-delivery) and delivery anemia was 54% and 44%, respectively. Maternal race and ethnicity but no other sociodemographic characteristics were associated with maternal anemia. Neonatal hematology was available for 114 newborns < 7 days old (50%; 52% male). The median (IQR) neonatal Hb was 16.7 g/dL (14.9, 18.0) and did not differ by sex, but it was lower among infants of mothers with vs. without delivery anemia (15.9 vs. 17.1, = 0.032) and those identifying as Black vs. Hispanic or other (16.0, 17.9, 17.0, respectively; = 0.003). Independent associations of maternal anemia and race and ethnicity with neonatal Hb were stronger in males and attenuated to null in females. Maternal anemia was highly prevalent and associated sex-specifically with neonatal Hb independent of maternal race and ethnicity. Future studies to replicate these findings with a more comprehensive panel of iron biomarkers are needed. Functional consequences of greater susceptibility to risk factors for low neonatal Hb in male infants need to be further investigated.