Trisomy 13 syndrome, also known as Patau syndrome, was first confirmed by Patau in 1960 to be caused by an extra chromosome 13, with an incidence of 1/6000-1/12000 in newborns. The main mechanism of trisomy 13 is the non-separation of chromosome 13 during the meiosis of germ cells, and the gametes carrying two chromosome 13s are fertilized with normal gametes to form embryos with three chromosome 13s. In addition, when one partner is a Robertsonian translocation carrier involving chromosome 13, there is a 1 in 6 chance that their gametes will acquire two chromosome 13s through meiosis, which will result in a translocated trisomy 13 embryo after fertilization; chimeric trisomy 13s originate from chromosome 13 nondisjunction in mitosis. The imbalance of gene dosage affects the normal development of the embryo, and because the number of genes carried on chromosome 13 greatly exceeds that of chromosome 21, its impact on embryonic development is also more severe than that of trisomy 21, so most trisomy 13s are aborted before birth. II. [Clinical manifestations] Patients with trisomy 13 often have severe multi-organ malformations. The central nervous system, head and facial malformations include microcephaly, total forebrain (78%-80%), agenesis of corpus callosum, microphthalmia, iris defect, cleft lip, cleft palate or both. 80% of children have cardiovascular malformations, with ventricular septal defect being the most common, and other atrial septal defect, patent ductus arteriosus, valve stenosis, etc. About 3/4 of them are complex cardiac malformations. Extremity anomalies include through palm, curved fingers, overlapping fingers in a clenched fist shape, and multiple fingers/toes are present in 75% of cases. In addition, duplicated kidneys, umbilical bulge, inguinal hernia, single umbilical artery, male cryptorchidism, and female bicornuate uterus may also be present. III. [Prenatal diagnosis] The prenatal diagnosis of trisomy 13 includes ultrasound and chromosomal examination. Full forebrain, central labyrinthine cleft and polydactyly are important ultrasound signs of trisomy 13, while definite diagnosis requires amniotic fluid or chorionic villus chromosomal examination, FISH can be used as an auxiliary method for rapid diagnosis, but only in specific cases. The prognosis of trisomy 13 is extremely poor, with 82% dying within one month after birth and only 5% surviving longer than six months, so once the diagnosis is clear, the pregnancy should be terminated at any gestational age. In standard trisomy 13, the risk of recurrence is low, but pregnant women over 35 years of age should be informed of the risk of other chromosomal aneuploidy in the next pregnancy; in translocation trisomy 13, chromosomal examination of both spouses should be performed to determine whether one of the spouses is a translocation carrier, and if the karyotype of the couple is normal, the risk of recurrence is low; if one of the spouses has a 13/13 Robertson translocation, only a monosomy 13 or trisomy 13 embryo can be formed, and the former cannot survive. If one of the couples is a 13/13 Robertson translocation, only a 13 monosomy or 13 trisomy embryo can be formed, the former is not viable, therefore the risk of a surviving fetus with translocation 13 trisomy is 100% and should be advised to be sterilized; if one of the couples is a 13 and other proximal chromosomes (14, 15, 21, 22) Robertson translocation, the risk of recurrence is <0.5%.