RENO, NEV. -- Ultrasound markers and biochemical findings can accurately predict trisomy 18 risk in fetuses with choroid plexus cysts, eliminating the need for amniocentesis in a large percentage of cases, Dr. Lorraine Dugoff reported.
She based this assertion on the initial results of an ongoing prospective collaborative project being conducted at seven centers in the United States and Canada.
Thus far, data have been collected for 157 fetuses with choroid plexus cysts measuring 3 mm or more in diameter, Dr. Dugoff said in a poster session at the annual meeting of the Society for Maternal-Fetal Medicine. None of the 149 cases with a normal karyotype had both ultrasound and biochemical markers for trisomy 18, and all 6 of the trisomy 18 cases had at least two abnormal ultrasound markers and abnormal biochemistry.
Choroid plexus cysts occur in 0.18%-2.5% of second-trimester fetuses and are associated with aneuploidy, particularly trisomy 18.
The single case of trisomy 21 identified in the study also had a positive ultrasound marker and findings on the triple screen suggestive of an increased risk for trisomy 21. There also was one fetus with a different abnormal karyotype,
The ultrasound evaluations assessed calvaria shape, a four-chamber view of the heart, outflow tracts, three-vessel cord, hands, feet, cisterna magna size, fetal biometry, and amniotic fluid volume.
Triple-screen biochemical testing also was done in each case, measuring maternal serum alpha-fetoprotein, human chorionic gonadotrophin, and unconjugated estradiol levels. Maternal serum levels of all three markers are depressed in trisomy 18.
Among the otherwise normal fetuses, the cysts were unilateral in 86 cases and bilateral in 63. In those who had trisomy 18 markers, the cysts were unilateral in three and bilateral in three others. The cyst was bilateral in the single trisomy 21 fetus.
The findings of this study support the practice followed at Dr. Dugoff's institution, the University of Colorado in Denver, which is to rely on the maternal serum triple screen and ultrasound screening. "We shouldn't be offering routine amniocentesis in these situations," as is done at some centers, Dr. Dugoff said.
COPYRIGHT 2001 International Medical News Group
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