FIRST 10,000 CHORIONIC VILLUS SAMPLINGS PERFORMED ON SINGLETON PREGNANCIES BY A SINGLE OPERATOR

Chorionic villus sampling (CVS) was performed in 10 000 consecutive si ngleton pregnancies by a single principal operator, working in two ins titutions. The procedure was performed between 8 and 32 gestational we eks: transabdominal (TA) sampling was carried out in 8479 cases and tr anscervical (TC) in 1521. Patients were referred for chromosomal risk in 89.1 per cent of cases, Mendelian disorders in 10.5 per cent, and D NA investigations for paternity or infectious agents in 0.4 per cent o f cases. The sampling success rate for both TA and TC techniques by th e second insertion was 99.8 and 99.2 per cent, respectively. TA sampli ng succeeded in a higher number of cases at the first insertion (98 pe r cent vs. 86.8 per cent) and was associated with smaller samples (<10 mg) in fewer cases (3.2 per cent vs. 4.9 per cent). Cytogenetic analy sis was highly successful (99.4 per cent) and accurate; however, in on e case a de novo structural rearrangement of chromosome 1 was not reco gnized. Mosaicism or rare trisomies were reported in 1.30 per cent of cases. Five diagnostic errors in DNA investigation (0.51 per cent) end ed with the birth of affected fetuses. Fetal loss through 28 weeks' ge station in the pregnancies intended to continue was 2.58 per cent; the rate increased with maternal age (1.22 per cent at less than 30 years to 3.8 per cent at 40 years or more), while gestational age affected the abortion rate only at 8 weeks (odds ratio=2.22, P<0.05). Rates of premature delivery, low birth weight, and perinatal mortality did not differ from the Italian standards. By comparison with the Italian Birt h Defects Registry data, no differences were found for the major malfo rmations, including transverse limb reduction defects (TLRDs) (4.34 vs . 3.28 x 10 000). Total malformations and TLRDs did not show any patte rn relation to either maternal age or gestational age. (C) 1998 John W iley & Sons, Ltd.