Biparietal diameter is usually less than 10cm belongs to the range of normal delivery, but it varies from person to person. Biparietal diameter is the distance between the two parietal bulges of the fetus, for the maximum transverse diameter of the fetal head, can be used to project the gestational age, is an important indicator to determine the size of the fetus. A full-term fetus has a biparietal diameter of 9.3 cm, and if the biparietal diameter of the fetus is close to or greater than 10 cm, the chances of a vaginal delivery will be reduced. Whether or not a woman can have a normal delivery is not only related to the size of the biparietal diameter, but also closely related to the condition of the woman’s pelvis, the force of labor after delivery, and the baby’s fetal heartbeat. Generally speaking, if the diameter of the fetus is around 9.3cm, and the fetal heart rate and labor force are normal, the baby can be delivered vaginally. If the biparietal diameter is close to or greater than 10cm, a normal delivery is less likely for a Chinese woman’s pelvis. Pregnant women need to visit regular hospitals during pregnancy, have their biparietal diameter checked regularly, and under the guidance of obstetricians, undergo relevant examinations and treatments to avoid adverse consequences.