Chromosomal abnormalities are not always present in all siblings and genetic counseling is recommended. Chromosomal abnormalities are categorized into chromosome number abnormalities and chromosome structure abnormalities. Number abnormalities are categorized into aneuploidy and aneuploidy abnormalities, and structural abnormalities include partial chromosome deletions, duplications, translocations, inversions, and so on. Genetic counseling is important for early detection and diagnosis of chromosomal abnormalities. Couples who have given birth to a child with a definite genetic disease or birth defect are at high risk for hereditary diseases and should undergo genetic counseling before pregnancy. Genetic counseling can provide couples with information about the disease in question, the mechanism of inheritance, as well as counseling on the risk of recurrence and counseling on family reproduction planning. Genetic counseling is recommended for high-risk couples, and rigorous obstetric and prenatal screening is required if pregnancy has already occurred.