COMBINING NUCHAL TRANSLUCENCY WITH UMBILICAL DOPPLER VELOCIMETRY FOR DETECTING FETAL TRISOMIES IN THE FIRST TRIMESTER OF PREGNANCY

Objective The aim of our study was to evaluate whether the combined us e of umbilical artery pulsatility index (UAPI) and nuchal translucency (NT) measurements would be useful in the prediction of fetal chromoso mal abnormalities at 10 to 13 weeks of gestation. Design A prospective study. Population and methods Five hundred and fifty-three consecutiv e women with singleton pregnancies between 10 and 13 weeks of gestatio n, who underwent chorionic villus sampling at our institution. UAPI an d fetal NT thickness were measured immediately before the invasive pro cedure. Pregnancies in which structural malformations had been detecte d by ultrasound were excluded. Results Using the 95th centile and 3 mm as the cutoffs for UAPI and NT, respectively, the detection rate for all chromosomal anomalies was 84.2%, with a false positive rate (1-spe cificity) of 6.6%, a positive predictive value of 31.3%, and a negativ e predictive value of 99.4%. Out of the 553 tested pregnancies 502 had both parameters within the normal range and only three of them (0.6%) were chromosomally abnormal; in six of the eight cases (75%) in which both parameters were abnormal a chromosome anomaly was present. Of th e 43 cases in which only one parameter was abnormal, 10 were chromosom ally abnormal (23.2%). Conclusions Our results suggest that the presen ce of chromosomal anomalies may be strongly suspected when an increase d NT thickness (NT greater than or equal to 3 mm) is associated with a n abnormally high UAPI at 10 to 13 weeks of gestation. The number of c ases studied is small, however, and these conclusions are tentative an d preliminary. The value of a single measurement of NT and UAPI for sc reening purposes needs to be substantiated by further investigation.