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CVS No Riskier Than Amniocentesis

Over time, rates of spontaneous pregnancy loss became similar for both procedures.

Invasive prenatal procedures remain necessary for the definitive diagnosis of fetal chromosomal abnormalities. Noninvasive methods such as triple analyte screening ultimately require a confirmatory invasive procedure before decisions regarding the pregnancy can be exercised. Amniocentesis remains the most common prenatal karyotyping procedure in the U.S., despite the disadvantage that it cannot be performed prior to 14 weeks’ gestation. Chorionic villus sampling (CVS), although a first-trimester procedure, is less frequently performed. In this retrospective study, the investigators tabulated rates of spontaneous pregnancy loss in patients who underwent CVS or amniocentesis compared with patients who did not undergo these procedures during a 20-year period (1983–2003) at a large U.S. prenatal diagnostic center. In their analysis, the authors considered maternal age, gestational age, and the year in which the procedure was performed.

A total of 9886 CVS and 30,893 amniocentesis procedures were performed during the 20-year interval. Although the overall loss rate was higher for CVS than for amniocentesis during the entire period, a greater progressive decrease in loss rate was observed over time for CVS. Thus, during the most recent time period included in the study (1998–2003), there was no significant difference in loss rates for CVS compared with amniocentesis (odds ratio, 1.03)

Comment: It seems almost fashionable for obstetricians to state that CVS is riskier than amniocentesis. In reality, results of an NIH-led study conducted when the procedure was first introduced showed that an estimated 0.8% excess risk for fetal loss associated with CVS compared with amniocentesis did not reach statistical significance. Moreover, although CVS is more difficult to master than amniocentesis, the risk for fetal loss shrinks as the experience of the practitioner grows. In South America and much of Europe, CVS is utilized far more commonly than in the U.S., where the procedure remains unavailable in many facilities. Still, driven by the unassailable logic of first-trimester screening, patient demand can be expected to increase.

— Sandra Ann Carson, MD

Published in Journal Watch Women's Health November 9, 2006

Citation(s):

Caughey AB et al. Chorionic villus sampling compared with amniocentesis and the difference in the rate of pregnancy loss. Obstet Gynecol 2006 Sep; 108:612-6.

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