Background: Down\u2019s syndrome is the most frequent chromosome aberration syndrome in newborns another well-known cause was related to the age of the mother. However, children with translocation Down\u2019s syndrome can be the offspring\u2019s of parents who carry balanced translocation chromosome. Objectives: (1) Study on the chromosomal abnormalities in Down\u2019s syndrome; and (2) analyse the risk of Down reproduction in couples who has a translocation chromosome t(Dq; 21q) or t(21q; Gq). Subjects and methods: The study was carried out on 157 Down\u2019s children who were between 1 day and 7 years of age, and 157 couples who were their parents from the National Institute of Pediatrics, pediatric departments of Bach Mai Hospital, Saint Paul Hospital and National Hospital of Obstetric and Gynecology. All participants were examined for the chromosome by culturing lymphocytes from peripheral blood. Results and conclusions: The rate of simple trisomy 21 was 92.4%; translocation type: 5.7%, and mosaic type: 1.9%. 154 couples (98.1%) have normal karyotype and 3 couples (1.9%) carry balanced translocation chromosome. 1 couple carried t(14q; 21q) and can have a Down offspring. 2 couples with t(21q; 21q) had 100% risk of having Down children. These 3 couples should have genetic counseling about Down syndrome.
Down\u2019s syndrome ; translocation Down\u2019s syndrome

The total 76 children from one month of age to fourteen years of age have been determined as phenotypic features and karyotypes of Down's syndrome. The distribution is as follow: typical trisomy is 69 cases (90%), translocation is 4 cases (5.26%), mosaism is 3 cases (3.95%). The mean maternal age at the birth of Down's patients was 30.8±2.2. The mean paternal age at the birth of Down's patients was 33.9±1.7. Maternal age distribution at the birth of Down's patients: The frequency was lowest in the mothers under 20 years old. It increases at age 25-29, then it decreased and increased again after the age 35-39. Chromosome studies have been made also on the patients, whose karyotypes are all normal (46,XX or 46,XY). The pedigrees of all patients were made. It has no one who has two patients in the same family
Down Syndrome ; diagnosis