The correct term for chromosomal abnormalities in pregnancy should be embryonic or fetal chromosomal abnormalities, which refers to the genetic mutations that occur during pregnancy when the embryo development is affected by external factors, such as exposure to toxic substances, radiation, certain drugs, viral infections, etc., which can affect the embryo, and parental genetic genes can also cause chromosomal abnormalities in the embryo, mainly including number abnormalities and structural abnormalities: 1. Number abnormalities: normal people have Some people can have chromosome number abnormalities, for example, patients with trisomy 21 have an extra chromosome 21; 2. Structural abnormalities: mainly chromosome ectopic, chimeric, inversion, deletion and overlap. Among them, embryonic chromosomal abnormalities are a common cause of spontaneous abortion, and 46%-54% of spontaneous abortions are related to embryonic chromosomal abnormalities. Fetal chromosomal abnormalities are often associated with stillbirths, or babies born with congenital malformations with high mortality rates and poor prognosis. The common fetal chromosomal abnormalities are trisomy 21, trisomy 18 and trisomy 13. Currently, chromosomal abnormalities are identified mainly through fetal screening. The method that can identify chromosomal abnormalities is fetal cell karyotyping after amniocentesis or umbilical cord blood puncture, and ultrasound can help assist in detecting fetal abnormalities or suspected abnormalities.