Cytogenetic analysis was carried out in PHA stimulated peripheral blood culture and confirmed using GTC-banding in a total of 382 children clinically suspected for Down syndrome to confirm the clinical diagnosis.
Results : The study constituted 84.82% of free trisomy 21, 8.90% translocation and 3.92% mosaics. In 9 [2.36%] cases regular trisomy 21 was associated with structural or numerical anomalies. Translocation was parentally inherited in 26.47% cases and maternal transmission was found twice as common as paternal. Investigations further revealed the ratio of male: female among the affected children to be more pronounced in male than female in all the groups. Interesting observation was majority of DS babies (91.6%) were born to younger mothers (20-35 yrs) compared to 8.4 in elderly mothers (>35 yrs.).
Conclusion : A higher incidence of DS in younger mother indicates the need for prenatal screening test irrespective of the past history for the incidence of the most common cytogenetic disorder like DS. In addition cytogenetic analysis helps to identify the origin of trisomy that provides important information for genetic counseling to the family.
Key Words : Down syndrome, non-disjunction, Prenatal Screening, trisomy 21.
Indian Pediatrics: 2008
