Mr. and Mrs. Mehtha have a 2 month old child with Down's syndrome. Karyotype of Mrs Mehtha shows translocation variety of Down syndrome. Which of the following investigations will you advise to the parents before the next pregnancy?

Karyotyping of Mrs. Annadurai has already been done and a translocation variety of Downs detected. Risk of recurrence however does not depend on mother's karyotype alone, but it also depends on the father's karyotype. Fathers karyotyping is therefore the test of choice prior to next pregnancy to determine the recurrent risk of having another child with Down's syndrome. Ref: In-Vitro Feilization By Kay Elder, 3rd Edition, Page 243 ; Textbook of Obstetrics By D.C.Dutta, 6th Edition, Page 107