Placental blood sinus is a normal physiological phenomenon that does not require intervention and cannot disappear. Placental blood sinus will increase in size, decrease in size or disappear with the increase of pregnancy weeks. Placental blood sinus refers to the chorionic center of the placenta in the center part of the chorionic villus without chorionic villi, placental parenchyma in the larger nearly round dark area, placental blood sinus is small, generally has no effect on the pregnant woman and the fetus, but the placental blood sinus is relatively large, and the occurrence of placenta previa, there is the possibility of vascular rupture of the placenta blood sinus, resulting in hemorrhage, is not conducive to the growth and development of the fetus. When the first ultrasound examination during pregnancy suggests placental blood sinus, the size of the placental blood sinus should be dynamically monitored and supervision should be strengthened for early detection of excessive placental blood sinus, which has a certain guiding effect on the termination of pregnancy, and if the placental blood sinus continues to increase and there is bleeding in the vagina, timely medical attention should be sought. In the presence of placental blood sinus, the ultrasound examination during pregnancy should be strengthened to assess the development of placental blood sinus, and observe the color of vaginal discharge.