Vasa previa is less common causes of antepartum hemorrhage. It is somewhat difficult to diagnose vasa previa prenatally by ultrasonography, and if placental vessel tearing occurs, serious maternal and perinatal mortality and morbidity can be developed. We experienced a case of fetal anemia that was related to rupture of placental vessel in vasa previa. A 34-year-old multiparous(1-0-0-1) woman was admitted for labor pain at 39 weeks gestation. On pelvic examination, Cervix dilatation 2cm, station -1 and effacement 70%, were noted. Except she received a cardiac valve operation 5 years ago, during her antenatal care, there was no specific findings. 2 hours after admission, the amniotic membrane ruptured spontaneously, presenting with 4 cm dilatation and 70% effacement of cervix, and +1 of station. At that time, suddenly fresh blood and blood clots gushed out of the vagina, and fetal tachycardia of 160~180 bpm were noted. Soon after fetal heart rate patterns revealed a sinusoidal pattern in intrapartum fetal monitoring. Pelvic exam showed 6 cm dilatation of cervix and +2 of fetal head descent, so she was moved to the delivery room to hasten vaginal delivery and to prevent intrapartum birth asphyxia. 10 minutes later, a male infant weighing 3640 grams was delivered with APGAR scores of 4 at one minutes and 5 at five minutes. The umbilical arterial cord pH was 6.81 and the neonate’s hematocrit was 37%. Suspected of having severe anemia the baby was transferred to the neonatal intensive care unit. Afterwards, the baby recovered completely following transfusion and oxygen treatment. Through a placenta study, we confirmed placental vessel tearing which likely caused massive vaginal bleeding during labor and led to neonatal anemia. Prenatal diagnosis of vasa previa using ultrasonography might be still limited, so during the labor progress it is important to be always cautious about sudden massive vaginal bleeding and/or changes in fetal heart patterns.