Chorionic villus sampling (CVS) offers rapid prenatal diagnosis of chr
omosomal disorders. We evaluated four methods for chromosomal analysis
of chorionic villi (three based on direct preparations and one on lon
g-term culture) in order to define a method which would provide good q
uality metaphases in sufficient numbers. The direct culturing method u
sing synchronisation and dissociation with dispase was as good as long
-term culturing. The optimal period of gestation for study was 10-12 w
k.