A woman with a baby of downs syndrome comes for preconceptional counseling. Karyotype of the affected baby shows nondisjunction. What is the chance of downs syndrome in the subsequent Pregnancy?
1%
5%
10%
25%
Recurrence RiskWith nondisjunction Down syndrome, the risk in a subsequent pregnancy would be 1% or the maternal age-related risk, whichever is higher. But in translocation Down syndrome, either parent may have translocation. In such cases, the risk to the offspring is 12% if the mother is the carrier and 3% if the father is the carrier. However, in the rare case of a carrier of a 21:21 translocation, the recurrence risk is 100%.Reference: Textbook of Obstetrics; Chapter 56; Prenatal diagnosis
General obstetrics