Preimplantation genetic diagnosis of cystic fibrosis (delta F508).

Cystic fibrosis is a common autosomal recessive condition caused by mutations in the cystic fibrosis transmembrane regulator gene. The major mutation is a three base pair deletion (delta F508). If both partners carry this deletion, the chance of having an affected child is 1 in 4. In vitro fertilization (IVF) with preimplantation genetic diagnosis allows the selection of the unaffected embryos only to be returned to the uterus. Preimplantation genetic diagnosis was attempted in 14 couples in which both partners carry the delta F508 deletion. A total of 22 cycles resulted in 170 normally fertilized embryos of which, 145 embryos were successfully biopsied and in 18 cycles, one or two unaffected embryos were transferred. A total of five clinical pregnancies established and at birth all five singletons have been confirmed as homozygous for the normal allele. From our experience, cleavage stage biopsy after in vitro fertilization provides sufficient embryos diagnosed as unaffected for transfer in this autosomal recessive disease. Also, pregnancy rates after the preimplantation diagnosis are similar to those with infertile couples. Prospects for applying preimplantation genetic diagnosis to autosomal dominant conditions, where incidences of having affected embryos would be higher, therefore, appear good.