Material and Method: The database of CVS procedures performed between January 2004 and August 2011 at Maharaj Nakorn Chiang Mai Hospital was assessed prospectively. Consecutive procedures during 10 to 14 gestational weeks were included into the present study. Indications, results, and complications of the CVS were extracted and analyzed.

Results: All 636 CVS procedures were successful. Indications for CVS were fetal karyotyping, DNA analysis for severe thalassemia disease, and for both in 36.5%, 50.6%, and 12.9%, respectively. However, 3.4% had inconclusive CVS result, and the second trimester prenatal diagnosis procedures needed to be done. There were five cases (0.8%) of fetal loss in the present study. Only two cases (0.3%) that fetal loss happened within two weeks of CVS procedures. Other minor complications such as vaginal bleeding and amniotic fluid leakage were found in 0.3 to 1.3% and had no long-term effect. No case with anomaly and procedure-related infection following the procedure was seen.

Conclusion: CVS is a safe and reliable prenatal diagnosis procedure in the first trimester. In experienced operators, fetal loss rate was less than 1%. However, a few cases will have inconclusive CVS results and may need a confirmation during the second trimester diagnostic procedures.

Keywords: Chorionic villous sampling, Prenatal diagnosis, Fetal loss