Chorionic villus sampling compared with amniocentesis and the difference in the rate of pregnancy loss.

OBJECTIVE: To compare loss rates following amniocentesis and chorionic villus sampling (CVS) over time.

METHODS: A retrospective cohort study of all amniocentesis and CVS procedures resulting in a normal karyotype from 1983-2003 at a single prenatal diagnostic referral center was conducted. Pregnancy loss rates for amniocentesis, CVS, and nonintervention groups (ie, those who had nuchal translucency screening or counseling, but no procedure) were compared using the chi 2 test. Year of procedure, maternal age, parity, race or ethnicity, and gestational age at procedure were controlled for in multivariable logistic regression models.

RESULTS: There were 9,886 CVS and 30,893 amniocentesis procedures performed during the study period that resulted in a normal karyotype. The overall loss rates were 3.12% for CVS and 0.83% for amniocentesis (P < .001). When examined by 5-year intervals, there was a statistically significant decrease in the CVS loss rate (P < .001) and a nonsignificant lesser decrease in the loss rate for amniocentesis over time. Although the pregnancy loss rate from CVS over the entire study period was higher than from amniocentesis (adjusted odds ratio 4.23, 95% confidence interval 2.29-7.81), in the most recent time period, 1998 to 2003, there was no difference between the two procedures (adjusted odds ratio 1.03, 95% confidence interval 0.23-4.52).

CONCLUSION: The loss rates for both amniocentesis and CVS at our institution have decreased over time. Because the decrease in loss rate for CVS has been greater, there is no longer a statistically significant difference between the two. These results are informative in both patient counseling and establishing widespread prenatal diagnostic and screening programs.