The large head of a baby in the 8th month of pregnancy may be caused by over-nutrition during pregnancy, congenital genetic factors, fetal malformation and so on. 1. Excessive nutrition during pregnancy: If the pregnant woman has excessive nutritional intake during pregnancy, the fetus grows faster and shows signs of macrosomia, with a large head and larger body limbs. 2. congenital genetic factors: if the parents have larger heads, then the baby’s head circumference may also be large. 3. Fetal malformation: If the baby’s neurological development is abnormal, the presence of brain bulge or hydrocephalus and other conditions may cause the baby’s head to be large. When the baby’s head circumference is large in the 8th month of pregnancy, you need to go to the hospital to do ultrasound to clarify the cause, and then take appropriate treatment under the guidance of the doctor. In addition, pregnant women should achieve balanced nutrition, good mood and moderate activity during pregnancy.