Effect of first-trimester ultrasound examination for chromosomal aberrations in women undergoing amniocentesis.

OBJECTIVE The purpose of this study was to assess the effect of first-trimester ultrasound examination for chromosomal aberrations in women who underwent amniocentesis. METHODS To evaluate trends in the indications of amniocentesis and the number of chromosomal aberrations, we reviewed all amniotic fluid samples from genetic amniocentesis processed by the Tama-Nagayama Hospital of Nippon Medical School from 1991 through 2005. The referral indications included first-trimester abnormal ultrasound finding. RESULTS A total of 1,054 women underwent genetic aminiocentesis in the first- to early second-trimester, and 1,063 amniotic samples were processed. The overall rate of chromosomal aberrations was 3.3% (35 of 1,063 samples), and the rate of aberrations remained unchanged during the study period. The number of cases with abnormal ultrasound finding increased from 5 (1.1%) in the first 5-year period to 46 (19.4%) in the last 5-year period (p<0.01). In contrast, the number of amniotic fluid samples per year tended to decline during the study period. CONCLUSION First-trimester ultrasound examination had a significant effect on our amniocentesis cases. The application of first-trimester ultrasound examination may be associated with a lower rate of invasive genetic testing.