Infertile men who carry a chromosomal translocation can be successfully treated with intracytoplasmic sperm injection (ICSI). However, such treatment carries a risk that a pregnancy with an abnormal karyotype will be induced. While in all previously published cases the outcome was favourable, we here report the first instance of a parental reciprocal translocation leading to a chromosomally unbalanced ICSI pregnancy. The fetus, one of a pair of dizygotic twins, was found to have trisomy for the short arm of chromosome 9. The parents opted for selective abortion of the affected twin.