MIDTRIMESTER CHORIONIC VILLUS SAMPLING - AN ALTERNATIVE APPROACH

OBJECTIVE: Our purpose was to audit midtrimester chorionic villus samp ling after a positive maternal serum screening test for autosomal tris omy. STUDY DESIGN: From January 1990 until July 1993 chorionic villus sampling was offered to all screened positive women. RESULTS: Five hun dred fifty-one mothers had chorionic villus sampling. The mean age was 31.7 years. The mean gestational age was 18.2 weeks. The mean time fo r direct karyotyping was 4.4 days and for culture results 20.2 days. R esults were obtained in 99.6% of samples: direct plus culture results in 94%, direct results alone in 2.3%, and culture results alone in 3.3 %. Fourteen pregnancies had abnormal karyotypes. There were five cases of placental mosaicism and one false-positive result. The loss rate w as 0.4%. CONCLUSION: Midtrimester chorionic villus sampling, which is easier to perform than cordocentesis, provides a rapid and reliable ka ryotype. The complication rate is comparable to that of other invasive procedures.