Fetomaternal hemorrhage (FMH) can cause severe morbidity. However, perinatal risk factors for long-term poor outcome due to FMH have not been extensively studied.To determine which FMH infants are likely to have neurological sequelae.A single-center retrospective observational study. Perinatal factors, including demographic characteristics, Kleihauer–Betke test, blood gas analysis, and neonatal blood hemoglobin concentration ([Hb]), were analyzed in association with long-term outcomes.All 18 neonates referred to a Neonatal Intensive Care Unit of Kagoshima City Hospital and diagnosed with FMH during a 15-year study period. All had a neonatal [Hb] <7.5g/dL and 15 of 17 neonates tested had Kleihauer–Betke test result >4.0%.Poor long-term outcome was defined as any of the following determined at 12month old or more: cerebral palsy, mental retardation, attention deficit/hyperactivity disorder, and epilepsy.Nine of the 18 neonates exhibited poor outcomes. Among demographic characteristics and blood variables compared between two groups with poor and favorable outcomes, significant differences were observed in [Hb] (3.6±1.4 vs. 5.4±1.1g/dL, P=0.01), pH (7.09±0.11 vs. 7.25±0.13, P=0.02) and base deficits (17.5±5.4 vs. 10.4±6.0mmol/L, P=0.02) in neonatal blood, and a number of infants with [Hb]≤4.5g/dL (78%[7/9] vs. 22%[2/9], P=0.03), respectively. The base deficit in neonatal arterial blood increased significantly with decreasing neonatal [Hb].Severe anemia causing severe base deficit is associated with neurological sequelae in FMH infants.