British Journal of Obstetrics and Gynaecology zyxwvut January 1997,Vol. 104,pp. 11-14 Combining nuchal translucency with umbilical Doppler velocimetry for detecting fetal trisomies in the first trimester of pregnancy *J. M. Martinez zyxwvuts PhD, *A. Borrell PhD, *E. Antolin MD, *B. Puerto MD, zyx **E. Casals MD, TJ. Ojuel PhD, *A. Fortuny PhD *Prenatal Diagnosis Unit, Department zyxwvutsr of Obstetrics and Gynaecology, **BiochemistryService, Hospital Clinic, and TBiostatistics Unit, University of Barcelona. Spain Objective The aim of our study was to evaluate whether the combined use of umbilical artery pulsatility index (UAPI) and nuchal translucency (NT) measurements would be useful in the prediction of fetal chromosomal abnormalities at 10 to zyxwvu 13 weeks of gestation. Design A prospective study. Population and methods Five hundred and fifty-three consecutive women with singleton pregnancies between 10 and 13 weeks of gestation, who underwent chorionic villus sampling at our institution. UAPI and fetal NT thickness were measured immediately before the invasive procedure. Pregnancies in which structural malformationshad been detected 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-specificity) of 6.6%, a positive predictive value of 31.3%, and a negative 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 the 43 cases in which only one parameter was abnormal, 10 were chromosomallyabnormal (23.2%) zyxwvu . Conclusions Our results suggest that the presence of chromosomal anomalies may be strongly suspected when an increased NT thickness (NT zyxwvu Z 3 mm) is associated with an abnormally high UAPI at 10 to 13 weeks of gestation. The number of cases studied is small, however, and these conclusions are tentative and preliminary. The value of a single measurement of NT and UAPI for screening purposes needs to be substantiatedby further investigation. INTRODUCTION The finding of a pathological umbilical Doppler pat- tern (absent or reversed end diastolic velocity) during second and third trimester pregnancies has been suggested to be associated with a higher incidence of chromosomal abnormalitie~'-~. Its application during the first trimester of pregnancy still remains in the research field, although it may prove to be a usehl tool to investigate certain first trimester abnormali- ties4s5. Recently we have found that umbilical artery Doppler measurements can be useful in the prediction of chromosomal abnormalities during early preg- nancy, showing an increased impedance to blood flow in such cases6. Increased fetal nuchal thickness also seems to be a well established ultrasonographic marker for the screening of fetal aneuploidies, partic- ularly when measured during the first trime~ter~-'~. Correspondence: Argentina 263, Atic 2", Barcelona 08023, Spain. Dr J. M. Martinez Crespo, Avda Repdblica Most pregnancies with chromosomally abnormal fetuses have signs of early functional and morpho- logical developmental disorders, reflected by a high rate of miscarriage and an early delay in intrauterine growth14J 5, and genetic disorders may affect fetal growth and p1a~entation'~J~. On this basis the aim of the present study was to investigate whether the combined use of fetal NT and fetal UAPI would increase the detection rate of fetal trisomies. METHODS This was a prospective study involving 553 women with viable singleton pregnancies referred to our prenatal diagnosis unit, undergoing chorionic villus sampling. The indications for fetal karyotyping were the risk of fetal aneuploidy because of advanced maternal age, previous offspring with chromosomal defects and risk of Mendelian disorders. Gestational age, determined by maternal menstrual history and z 0 RCOG 1997 British Journal of Obstetrics and Gynaecology 11