Chorionic villus sampling for prenatal diagnosis in Wales using DNA probes--5 years' experience

Chorionic villi were sampled from 125 women who requested prenatal diagnosis, either for genetic disorder or because of advanced maternal age. Of these, 105 samples were obtained by the transcervical route and 20 were obtained by the transabdominal approach. The sampling success rate was 97 per cent (122/125). The mean maternal age of the patients was 31 years (range 17-44) and the mean gestational age at which the chorionic villus sampling was performed was 10 weeks (range 7-13 weeks). Seventy-four of these diagnoses involved the use of DNA markers. The minimal size of the sample used for DNA diagnosis was 5 mg. Maternal contamination was detected in two samples. A diagnosis was provided on all but two samples. The fetal loss rate was high initially but fell to 1.9 per cent in 1988.