Small head size in late fetal life is not necessarily an intellectual problem, it needs to depend on the cause of the small head size. Generally the head circumference of the fetus is related to malnutrition and growth retardation. Most of the malnutrition is physiological factors, then generally will not affect the intelligence of the fetus. If there are pathological factors, such as microcephaly, chromosomal or genetic abnormalities, then it is easy to affect the intellectual development of the fetus. To rule out pathologic factors, prenatal screening should be done based on cranial CT and intelligence testing. Microcephaly is a condition in which the brain weight is significantly lighter than that of a normal child, the cerebral gyrus is too small or there is no cerebral gyrus at all, and there are obvious developmental abnormalities in the brain. By perfecting prenatal screening during pregnancy, abnormalities that affect mental development will be detected early. It is important for women to undergo regular labor and delivery tests during pregnancy so as to reduce the risk of fetal low intelligence, and if problems with fetal head circumference are detected, it is recommended that prompt medical attention be sought.