Background: A proportion of cases with repeated abortion are caused by chromosomal abnormality in one of the parents. Several studies have been done to determine the role of chromosomal abnormalities in couples with repeated fetal loss in various countries. None of these studies was done in the Arab Peninsula. Material and Methods: Cytogenetic study was done for 193 consecutive Saudi couples who presented with repeated abortion at the King Khalid University Hospital in Riyadh, Saudi Arabia. Results: We found that the frequency of chromosomal abnormalities was not significantly different from that reported worldwide. The nature of those abnormalities and their relation to the obstetric history of cases were discussed. Approximately 15%-20% of clinically recognizable pregnancies end in spontaneous abortion. Conclusion1,2 The incidence of chromosomal abnormalities in those abortions is as high as 50%.3 A modest but clinically important proportion of spontaneous abortions is caused by a balanced chromosomal aberration in one of the parents. [4][5][6][7][8] This results from the production of gametes and embryos with unbalanced chromosome sets.9,10 The clinical consequences of such abnormal gametes include sterility, repeated abortions, and giving birth to malformed children. 11,12Several studies have been done in various countries to determine the contribution of chromosome abnormalities in parents with fetal wastage. 13 To our knowledge, no such studies have been done in the Arabian Peninsula. The aim of this study was to assess the frequency and nature of chromosomal aberrations that contribute to the occurrence of repeated abortions in Saudi Arabia. This should assist physicians in Saudi Arabia and other neighboring countries by increasing their awareness of the frequency of cytogenetic abnormalities in cases with repeated abortions. It also provides figures for comparison with other countries and research centers. Materials and MethodsThis study included all Saudi couples with repeated abortions who were referred for cytogenetic studies between December 1994 and December 1998 at King Khalid University Hospital in Riyadh, Saudi Arabia. All cases were ascertained to have had two or more spontaneous abortions. Couples who were referred because of having previous children with congenital anomalies and abortions were not included in the study. The obstetric history of couples was either recorded on the request form or retrieved from the files of patients.For routine cytogenetic analysis, 0.3 mL of peripheral blood was incubated in complete lymphocyte culture medium (10% fetal bovine serum in RPMI 1640, with 0.15% phytohemagglutinin and 1% Penstrept in 5% CO 2 incubator at 37°C for three days). Metaphases were harvested by adding colcemid for 20 minutes, followed by hypotonic KCl treatment for 5 minutes and fixation, using standard 3:1 methanol-acetic fixative (all the reagents were from GIBCO Life Technologies Ltd., Paisley, Scotland). The high-resolution study was done by synchronization, using methotrexate (10 -7 M...