UMBILICAL DOPPLER VELOCIMETRY IN FETUSES WITH TRISOMY-18 AT 10-18 WEEKS GESTATION

The aim of our study was to obtain measurements of the umbilical arter y pulsatility index (PI) in pregnancies before invasive procedures for prenatal diagnosis, in order to investigate its potential prognostic value in predicting trisomy 18. We performed a prospective study inclu ding 1785 consecutive women from 10 to 18 weeks with singleton pregnan cies undergoing chorionic villus sampling (n=559) or genetic amniocent esis (n=1226) in our unit. Doppler measurements were performed transva ginally (tenth to 13th week of gestation) or transabdominally (14th to 18th week of gestation) immediately before the invasive procedure. In 7 out of 10 fetuses subsequently diagnosed as trisomy 18, the PI was above the 95th centile, providing a detection rate of 70 per cent, a s pecificity of 95.1 per cent, a positive predictive value of 7.7 per ce nt, and a negative predictive value of 99.8 per cent. When the 90th pe rcentile was assayed as a cut-off, the efficacy of PI as a marker of t risomy 18 yielded a sensitivity of 90 per cent and a specificity of 90 .4 per cent, with a positive predictive value of 5.2 per cent and a ne gative predictive value of 99.9 per cent. We suggest that although the use of a single PI measurement for screening purposes needs to be con firmed by further investigation, trisomy 18 fetuses show an abnormal i ncrease in umbilical PI in the first half of pregnancy, and its relati on to the early onset of fetal growth retardation needs to be further explored. (C) 1997 by John Wiley & Sons, Ltd.