en Pathology Pathology Original Research Original Research The indications and results of cytogenetic analysis of 521 amniotic cell cultures performed at 13-16 weeks of gestation were evaluated in this study. 507 fetuses (97.3%) were cytogenetically normal, 14 (2.7%) had unbalanced karyotypes, and 2 fetuses were found to have major abnormalities, one with anencephaly detected by measurement of alpha -fetoprotein levels in amniotic fluid and ultrasonography, and the other with a full mutation at the FMRl locus detected by molecular techniques. The unbalanced karyotypes included 2 cases each of trisomy 21, trisomy 18, triple X, 47 XXY and mosaicisms and 4 cases of various chromosomal abnormalities. 225 tests were performed for women 35 years of age or over, 6 (2.4%) abnormal karyotypes were detected, showing a 6 - fold increase over the general population. This risk was even higher (2/23,8.7%) among those parous aged >35 y who had a previous history of offspring with chromosomal aberrations. 5 of 32 (15.65%) fetuses whose parent was a carrier of a balanced chromosomal translocation or a small chromosomal marker (in one case), had unbalanced chromosomal aberrations. There were 7 cases of spontaneous abortion within 4 weeks after amniocentesis, one of which was a case of 46 XY, t (1421), + 18. Excluding this case, the rate of abortion (6/521, 1.3%) was quite below the expected rate of 2.1 % for spontaneous abortion in the 2nd trimester of pregnancy. Our data indicates that amniocentesis performed at 13-16 weeks is a safe, reliable procedure for detection of fetal chromosomal abnormalities in Iran, and we strongly recommend it for those parous at risk. 161 166 http://mjiri.iums.ac.ir/browse.php?a_code=A-10-298-382&slc_lang=en&sid=1 A A. KARIMI-NEJAD 20031947532846004572 20031947532846004572 Yes From the Karimi-Nejad Pathology and Genetic Center, Tehran, I.R. Iran. N LASHGARIAN 20031947532846004573 20031947532846004573 No MH KARIMI-NEJAD mhkarimi@mavara com 20031947532846004574 20031947532846004574 No