(1) Clinical manifestations: The malformations and clinical manifestations of the children are much more severe than in trisomy 21. Craniofacial deformities include small head, defective forehead and forebrain development, small eyes, often with iris defects, wide and flat nose, 2/3 of affected children have cleft upper lip and often cleft palate, low ear position, auricular deformity, small jaw, other common polydactyly (toe), fingers overlapping each other, heel protruding backward and midfoot convexity, forming the so-called rocking chair bottom foot. Males often have scrotal malformations and cryptorchidism, while females have clitoral hypertrophy, double vagina, bicornuate uterus, etc. Malformations of the brain and internal organs are very common, such as anosmia, ventricular or atrial septal defects, patent ductus arteriosus, polycystic kidneys, hydronephrosis, etc. Deafness is caused by defects of the inner ear spirals. Mental retardation is seen in all patients and is severe, with seizure-like epilepsy and hypotonia in the longer surviving children. (2) Cytogenetics and genetic counseling: 80% of cases are free trisomy 13 with karyotype 46, XX (or XY), +13, and the rest are chimeric or translocated. The chimeric type is generally less symptomatic, and the translocated type is usually predominant with the 13 and 14 rosette translocations. Patients have a t(13q14q) translocation chromosome with karyotype 46, -14, +t(13q14q), which results in an extra long arm of 13. When one of the two parents is a balanced translocation carrier, the risk of producing an affected child is no more than 5% or 1% because the vast majority of abnormal fetuses are aborted and die . If one of the two parents is a 13q13q translocation carrier, the miscarriage rate is 100% because only trisomy or monosomy congeners can be produced. (3) Etiology and prognosis: Since little is known about the factors involved in the development of trisomy 13, advanced maternal age may be one of the causes, with a mean age of 31.6 years for mothers and 34.6 years for fathers of affected children. In addition, it is well documented that 79% of cases are gestated during the cold season (September-February), 45% of children die within the first month of life, 90% die within 6 months, less than 5% survive to 3 years of age, and the average life expectancy is 130 days.