The width of the lateral ventricle is more stable from 16 to 38 weeks of gestation, about 6-8 mm. The fetus develops rapidly at 24 weeks and the width of the lateral ventricle may increase, but the cerebrospinal fluid will be absorbed to some extent, especially at 32 weeks when the cerebrospinal fluid is absorbed the fastest, and a mildly widened fetus can absorb itself back to normal. However, widening of the lateral ventricle can also be seen in the following cases: 1. Fetal chromosomal abnormalities: If the fetus has chromosomal abnormalities, it will lead to abnormal development of the nervous system in the brain, which will easily cause widening of the lateral ventricle. If the widening persists or becomes more serious, the fetus will develop brain malformation or even neurological malformation. If the widening of the lateral ventricle is diagnosed to be caused by fetal malformation, the pregnancy needs to be induced and terminated as soon as possible because this condition is generally incurable; 2. Fetal hydrocephalus or intracranial hemorrhage: both of these conditions are related to the mother, and if the pregnant woman has high blood pressure, head tumor or drug abuse during pregnancy, it will cause intracranial hemorrhage and hydrocephalus in the fetus, it may also be related to the fact that the pregnant woman did not take folic acid in the early stage, and the mother should actively treat her disease; 3, intrauterine infection: during pregnancy the pregnant woman may be infected with bacteria or viruses, common viral infections are cytomegalovirus, syphilis, mumps virus, etc., which can easily cause defects in fetal brain development, thus causing widening of the fetal lateral ventricle.