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ISRCTN38014610.

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We report the first established pregnancy using preimplantation genetic diagnosis in order to avoid chromosomal imbalance in the progeny of a woman carrying a large inversion of chromosome 5. This is also the first time where it has been possible to study the distribution of balanced and unbalanced gametes in a female inversion carrier. In total, 23 embryos were biopsied in two separate treatments and analysed by fluorescent in-situ hybridization. Of these, 10 were unbalanced, nine were balanced and for four the analysis was inconclusive. The diagnostic procedure was performed within 3.5 h. This allowed the biopsied embryos to be transferred the same day as the biopsy was taken (day 3). Two embryos were transferred each time, and in the second treatment a twin pregnancy with two chromosomally balanced fetuses was established. Healthy twins were delivered at 34 weeks of gestation.

We report the first case of preimplantation genetic diagnosis used in order to avoid chromosomal imbalance in the progeny of a woman mildly affected by DiGeorge syndrome and carrier of a microdeletion of chromosome 22q11.2. In total, seven embryos were biopsied in three separate treatments and analysed by fluorescent in-situ hybridization (FISH). Of these, four were carrying the deletion, two were normal and in one the analysis was inconclusive. The diagnostic procedure was performed within 5 h. This allowed the biopsied embryos to be transferred the same day as the biopsy was taken (day 3). Two embryos were transferred in the third treatment, but no pregnancy was established. Patients with a 22q11 microdeletion, who have a 50% risk of transmitting the deletion to their offspring, can now be offered preimplantation genetic diagnosis using FISH for the detection of a 22q11 deletion.

We have tested and subsequently successfully applied a single‐needle approach to obtain blastomere biopsies from human preimplantation embryos for preimplantation genetic diagnosis (PGD). The method was first evaluated in a mouse system and shown to be compatible with a high degree of in vitro and in vivo development of biopsied mouse embryos. Furthermore, we showed that biopsied mouse embryos after transfer to recipient mice underwent implantation, normal development and delivery. Litters were followed through puberty and adulthood and shown to be normal with regard to sexual function and also a panel of biochemical and morphological parameters including organ histology. Successful human preimplantation diagnosis, followed by pregnancies and birth of healthy babies, was established with two out of three couples carrying a risk to transmit chromosomal abnormalities leading to severe disease. This is the first report of the successful use of a single‐needle approach in human PGD. Considering its simplicity, we conclude that the single‐needle approach is an attractive alternative for biopsies in PGD. Copyright © 1998 John Wiley & Sons, Ltd.

PGS seems to be a good method for selecting against chromosomally abnormal embryos but not for determining an embryo's exact chromosomal constitution.

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