ULTRASONOGRAPHY FOR MEASURING NUCHAL TRANSLUCENCY AND PRENATAL GENETIC SCREENING

Abstract

INTRODUCTION: Routine ultrasonography at the beginning of pregnancy enables a better assessment of gestational age, early detection of multiple pregnancies and early detection of clinically unsuspected fetal malformation. After this first screening it is recommended in case of changes, more accurate examinations to diagnose chromosomal abnormalities. OBJECTIVE: To analyze the effectiveness of the ultrasound method for measuring nuchal translucency (NT) in screening for chromosomal abnormalities confirmed by chorionic villus biopsy or amniocentesis and to define the efficiency of NT as a diagnostic test for fetal abnormalities, to establish the most frequent chromosomal abnormalities and to verify whether NT can be incorporated as aneuploid trace elements. METHODS: This is an observational, descriptive, retrospective analytical study of pregnant women attended from 2007 to 2017 at the Fértile Clinic to perform nuchal translucency ultrasound screening performed at gestational age between 11th and 13th weeks and six days of age of pregnancy. NT measurement was considered increased when it was < 2.5 mm. Fetal karyotype was established by cytogenetic analysis of material obtained by chorionic villus sample or amniocentesis. RESULTS: A total of 219 pregnant women were studied, among them 216 with NT alterations (> = 2.5 mm), submitted to confirmation by chorionic villus biopsy and 113 normal ones. Sensitivity: 100%, Specificity: 97,3%, Positive Predictive Value (PPV): 49%, Negative Predictive Value (NPV): 100% and accuracy: 49.8%. The most prevalent maternal age was 18 to 35 years, with normal karyotype exams and confirmation by chorionic villus biopsy was chosen and the main karyotype change was 47 XX + 21. CONCLUSION: NT as a diagnostic test for fetal aneuploidies presented 100% sensitivity, 100% NPV, 97,3% specificity, PPV 49% and accuracy 49.7%. The most frequent fetal chromosomal abnormality was 21 (Down syndrome) trisomy 47 XX + 21. Considering that the criterion of the important diagnostic test for disease screening is sensitivity, NT should be incorporated as such, since sensitivity was full in this study.