OBJECTIVE This case report aims to review the literature on fetomaternal hemorrhage, its prevalence, etiology, clinical presentation, and diagnosis through this case. Case(s) A primigravida of 38+5 weeks of gestation consulted for absent fetal movements. Cardiotocography showed fetal tachycardia, alternating with a pseudo-sinusoidal pattern. An emergency cesarean section was performed due to suspected fetal distress, and the newborn presented an hemoglobin of 4.6 g/dl at birth. A Kleihauer-Betke test was performed diagnosing a fetomaternal hemorrhage, requiring neonatal care without further consequences. CONCLUSION Fetomaternal hemorrhage is rare and often of unknown etiology. In this case, it was diagnosed post-birth. Recognizing cardiotocography patterns and clinical presentations is crucial to reduce fetal consequences, as fetal hemoglobin at birth is a prognostic factor for neonatal morbidity and mortality.