Alternative to Routine Amniocentesis Proposed.

MAUI, HAWAII -- A three-pronged strategy to screen for fetal abnormalities using two ultrasound examinations and triple-marker serum screening may be safer and less expensive than routinely offering amniocentesis to older women, Dr. Manuel Porto said at a conference on ob.gyn. ultrasound sponsored by the University of California, Irvine.

In a hypothetical group of 10,000 pregnant women aged 35 or older, the triad of tests would be half as expensive as routine amniocentesis (saving almost $5 million), cause half as many deaths in normal fetuses (24 instead of 50), and would miss few cases of serious aneuploidy, he said.

Routine amniocentesis would detect 100% of all chromosomal abnormalities if all women took the test, but many decline. The alternative triad would detect 94% of trisomy 21 cases and 87% of other major structural trisomies, including about 80% of the sex chromosome abnormalities, said Dr. Porto, director of maternal-fetal medicine at the university.

The alternative strategy starts with a first-trimester ultrasound between 10 and 13 weeks' gestation at an estimated cost of $100 per scan to confirm gestational age and assess nuchal translucency Women with an abnormally thick nuchal translucency would be offered chorionic villi sampling (CVS) or early amniocentesis at estimated costs of $1,000 or $750, respectively

Dr. Porto estimated that 10% of fetuses would have abnormal nuchal translucencies, although results of most studies suggest rates closer to 5%-7%. He assumed that 1% of women choosing CVS would lose their pregnancies, and the test would detect 40% of Down syndrome fetuses, although data suggest the detection rate is closer to 70%-80%, he said at the meeting, also sponsored by Long Beach Memorial Medical Center.

In the second stage of the screening triad, ...