As reported by Medscape web site, May 31, 2004.

Noninvasive Prenatal Testing Cuts Amniocentesis Use

NEW YORK (Reuters Health) May 31 - A study released today suggests that advances in noninvasive prenatal screening -- maternal serum screening and ultrasound -- have led to the more selective use of amniocentesis and chorionic villus sampling (CVS) to detect fetal anomalies.

"Ideally," the authors say, prenatal aneuploidy screening will reach levels of efficacy such that invasive testing would only be needed to confirm, or precisely define, a chromosomal abnormality detected noninvasively.

"Our results show that there has been substantial progress toward this objective," Dr. Peter A. Benn from the University of Connecticut Health Center in Farmington and colleagues write in the June issue of Obstetrics and Gynecology.

In the study, the investigators reviewed all amniotic fluid and CVS samples processed at a single laboratory over a 12-year period (1991-2002). They also evaluated trends in the use of prenatal testing, reasons for referral, and cytogenetic abnormalities identified.

Despite an increase over the study period in the number of women becoming pregnant after age 35, there was a decline of more than 50% in the number of women undergoing amniocentesis or CVS. This fell from 1,988 in 1991 to 933 in 2002.

There also was a significant 68% drop in the number of women referred for invasive prenatal testing solely on the basis of their age (from 1,314 in 1991 to 423 in 2002).

Despite the decline in amniocentesis and CVS, the number of Down's syndrome fetuses detected increased from 20 cases in 1991 to 31 in 2002.

However, this accounts for only about half of the affected pregnancies present in the population, the authors note. The proportion detected is "less than might have been expected, given the improvements in screening over time."

The researchers thus conclude that it will be important to determine whether this is a result of patients' attitudes toward prenatal testing, a desire not to know whether the fetus is affected, or whether there are "substantial access barriers" to screening.

Obstet Gynecol 2004;103:1255-1260.