P17.11: First trimester screening for chromosomal abnormalities by fetal nuchal translucency in a Brazilian population

Abstract

Objectives:The aim was evaluated the preliminary results of an implementation of assessment of risk in a tertiary center hospital in Brazil.Methods: This was a prospective study of 1.555 singleton pregnancies with a live fetus at 10-14 weeks of gestation attending for routine antenatal care in a tertiary hospital in Brazil. Fetal crown-rump length (CRL) and NT thickness were measured and the risks for trisomy 21 were calculated by a combination of maternal age and fetal NT according to the software provided by The Fetal Medicine Foundation. Results: The maternal age ranged from 13 to 48 years (median, 30 years, SD +7.6) whereas 15.5% were younger than 20 years (144/931), 32.0% and 7.4% older than 35 years (506/1555) and 40 years old. The body mass index was greater than 30 kg/m 2 in 10% of these pregnant women and 61% from 18.5-24.9 kg/m 2 . Nulliparous and primiparous were found in 48.9% and 29.8% respectively. The distribution of NT measurements revealed that 64.5% and 11.6% of the population had measurements above the 50 th and 95 th percentile for gestational age with no difference among the six members of the group. The estimated risk was greater than 1 : 300 and 1 : 100 in 57 patients (3.7%) and in 16 patients (1.0%) respectively. Based on the distribution of maternal age, it was expected 2.6 cases of trisomy 21 and approximately the same number of other chromosomal defects. In this population, the invasive procedure was performed in 100 pregnant women and there were three cases of autosomal trisomies, one of trisomy of sex chromosomes, one case of Turner syndrome and two cases of structural chromosomal alterations. Of this population, 85.7% (6/7) had NT > 95 th percentile for gestational age and 42.8% (4/7) were younger than 35 years old. Conclusions:The discriminative capacity of nuchal translucency measurement makes it a useful tool in screening for chromosomal abnormalities. Objectives: To study the value of nuchal translucency (NT) measurement in the screening for chromosomal abnormalities at 11-14 weeks of gestation. Methods: A total of 5077 fetuses were studied consecutively at Vitoria MedifetUS, Vitoria, Brazil. In 370 cases a cytogenetic study was performed on material obtained from a biopsy of the chorionic villus, and in 4707 cases the result was based on the postnatal phenotype. In addition to the routine ultrasonographic examination, all fetuses were submitted to measurement of the NT thickness. For statistical analysis Student's t test and ANOVA were used. Sensitivity, specificity, positive and negative predictive values, false-positive rate and likelihood ratio were calculated. Results: Seventy-nine cases of chromosomal abnormalities occurred. Of these abnormal cases, NT measurement was above the 95 th percentile in 60 (sensitivity of 75.9%) and specificity was 98.0%, positive and negative predictive values were 38.0% and 99.6%, respectively, false-positive rate was 2.0% and likelihood ratio was 38.7. Conclusions: Our results suggest that the presence of chromosomal abnormalities may be stro...