RM is associated with a higher incidence of chromosomally abnormal embryos, of which some are able to develop to the blastocyst stage. IVF plus PGD is an important step in the management of these couples, but the technique has to move towards a full chromosome analysis.

Previous studies have shown that patients with deletion of distal human chromosome arm 8p may have congenital heart disease and other physical anomalies. The gene encoding GATA-4, a zinc finger transcription factor implicated in cardiac gene expression and development, localizes to chromosome region 8p23.1. To examine whether GATA-4 deficiency is present in patients with monosomy of 8p23.1 with congenital heart disease, we performed fluorescence in situ hybridization (FISH) with a GATA4 probe on cells from a series of patients with interstitial deletion of 8p23.1. Four individuals with del(8)(p23.1) and congenital heart disease were found to be haploinsufficient at the GATA4 locus by FISH. The GATA4 gene was not deleted in a fifth patient with del(8)(p23.1) who lacked cardiac anomalies. FISH analysis on cells from 48 individuals with congenital heart disease and normal karyotypes failed to detect any submicroscopic deletions at the GATA4 locus. We conclude that haploinsufficiency at the GATA4 locus is often seen in patients with del(8)(p23.1) and congenital heart disease. Based on these findings and recent studies showing that haploinsufficiency for other cardiac transcription factor genes (e.g., TBX5, NKX2-5) causes congenital heart disease, we postulate that GATA-4 deficiency may contribute to the phenotype of patients with monosomy of 8p23.1.

Embryos with certain types of chromosomal abnormalities were negatively selected during preimplantation embryo development. Despite this selection, a remarkable percentage of chromosomally abnormal embryos can develop normally to blastocyst stage with high probability of implantation and pregnancy.

Implantation failure (IF) is defined as three or more failed IVF attempts, and preimplantation genetic diagnosis (PGD) is being used in these patients to improve IVF outcome. PGD was performed in 49 implantation failure patients with a mean number of 4.2 +/- 1.6 previous IVF failures, and in nine fertile controls. Fluorescence in-situ hybridization (FISH) on blastomeres from biopsied day 3 embryos was performed for chromosomes 13, 16, 18, 21, 22, X and Y. There was a significantly higher rate of chromosomal abnormalities (67.4%) compared with controls (36.3%). In 57 cycles, a pregnancy rate of 34.0% and an implantation rate of 19.8% was observed in implantation failure patients compared with controls (33.3 and 24.1% respectively), with all the pregnancies in the implantation failure group coming from the transfer of at least one chromosomally normal blastocyst on day 5. It is concluded that in IVF patients, use of PGD along with blastocyst transfer improves IVF outcome.