During the 14-38 weeks of gestation, the fetal lateral ventricular width is usually a relatively constant value, with a mean value of 7 mm and an upper limit of 10 mm for normal, 10-15 mm for mild lateral ventricular widening, and greater than or equal to 15 mm for severe lateral ventricular widening or hydrocephalus. Significant widening of the lateral ventricles may indicate chromosomal abnormalities in the fetus. The probability of mild lateral ventricular widening in normal fetuses is very low, while the prevalence of fetuses with trisomy 21 (chromosomal abnormalities disease) is much higher than normal fetuses, indicating that the widening of the lateral ventricles may indicate fetal chromosomal abnormalities, as well as the possibility of distant neurological developmental abnormalities, which are more difficult to cure. Some fetuses with simple mild lateral ventricular widening can absorb on their own and will gradually decrease with growth and development, with good prognosis; those who cannot absorb on their own can be born with ventricular drainage; in case of severe lateral ventricular widening and hydrocephalus, it indicates high risk of brain tumor, viral infection, central nervous system disease, chromosomal abnormalities, etc., and requires clear etiology before choosing postnatal treatment or termination of pregnancy.