If the first pregnancy is normal, the probability of chromosomal abnormalities in the second pregnancy is relatively low, but the possibility of chromosomal abnormalities cannot be completely ruled out because the occurrence of fetal chromosomal abnormalities is multifactorial. If there is a family history of chromosomal abnormalities in the couple’s family, the chances of the fetus suffering from chromosomal abnormalities after pregnancy are the same for the first and second child. However, the probability of a fetus having a chromosomal abnormality is different for different inheritance modalities, such as dominant and recessive inheritance. For example, in autosomal recessive inheritance, if both husband and wife carry the disease-causing gene, the probability of the affected child having a chromosomal disorder is 1/4, independent of the number of fetuses. However, if there is no genetic system diseases, solely from the embryonic development point of view, the first normal, does not affect the chances of chromosomal abnormalities in the second child, embryonic chromosomal abnormalities are mainly affected by the following factors, life should be avoided as much as possible: 1, physical factors: pregnant women in the early stages of pregnancy, if exposed to radiation, ionizing radiation, may cause chromosomal abnormalities, the probability of incidence of increased with the dose of rays and increase, if a pregnant woman is subjected to If the pregnant woman suffers serious radioactive damage, the risk of chromosomal abnormalities in the fetus is higher, but it is impossible to estimate the exact value; 2, chemical factors: taking drugs with teratogenic effects during pregnancy, such as antitumor drugs, antiepileptic drugs, and sedative and tranquilizers, etc., which may lead to chromosomal abnormalities in the fetus; 3, biological factors: if you suffer from a special viral infections during pregnancy, such as rubella, measles, cytomegalovirus, toxoplasmosis, mumps, and other viruses, you should try to avoid them as much as possible. Biological factors: If you are infected by special viruses during pregnancy, such as rubella virus, measles virus, cytomegalovirus, toxoplasma gondii, mumps virus, etc., it may lead to chromosome mutation in the fetus and cause chromosome abnormality diseases; 4. Pregnant women are required to undergo regular obstetric examinations for screening of chromosomal disorders, such as Down’s syndrome screening, non-invasive DNA screening, and possibly amniocentesis if necessary. If the test reveals abnormal development of the fetus, the pregnancy needs to be terminated if necessary.