A simple technique for obtaining high quality chromosome preparations from chorionic villus samples using FdU synchronization

A fluorordeoxyuridine (FdU) synchronization technique was applied to 30 chorionic villus samples (CVS) from patients undergoing first trimester fetal diagnosis. The villi were incubated for 15 h in the presence of FdU. The block in DNA synthesis was subsequently released using thymidine and after an additional 5 h of incubation the mitotic cells were arrested in metaphases using a high concentration of colcemid. This method results in improved morphology of the chromosomes and a high mitotic index. A diagnostic chromosome analysis could be obtained in each clinical case using at least 15 well‐spread metaphases. G‐banded karyotypes were prepared of four metaphases in each case. The diagnostic procedure was completed within 48 h from the time of CVS. Use of this technique significantly improves the success rate of ‘direct’ chromosome analyses from CVS in a busy cytogenetic laboratory.