Isolated Increased Nuchal Translucency in First Trimester Ultrasound Scan: Diagnostic Yield of Prenatal Microarray and Outcome of Pregnancy

Background: Increased nuchal translucency (NT) is associated with aneuploidy. When the karyotype is normal, fetuses are still at risk for structural anomalies and genetic syndromes. Our study researched the diagnostic yield of prenatal microarray in a cohort of fetuses with isolated increased NT (defined as NT ≥ 3.5 mm) and questioned whether prenatal microarray is a useful tool in determining the adverse outcomes of the pregnancy.Materials and Methods: A prospective study was performed, in which 166 women, pregnant with a fetus with isolated increased NT (ranging from 3.5 to 14.3 mm with a mean of 5.4 mm) were offered karyotyping and subsequent prenatal microarray when karyotype was normal. Additionally, all ongoing pregnancies of fetuses with normal karyotype were followed up with regard to postnatal outcome. The follow-up time after birth was maximally 4 years.Results: Totally, 149 of 166 women opted for prenatal testing. Seventy-seven fetuses showed normal karyotype (52%). Totally, 73 of 77 fetuses with normal karyotype did not show additional anomalies on an early first trimester ultrasound. Totally, 40 of 73 fetuses received prenatal microarray of whom 3 fetuses had an abnormal microarray result: two pathogenic findings (2/40) and one incidental carrier finding. In 73 fetuses with an isolated increased NT, 21 pregnancies showed abnormal postnatal outcome (21/73, 28.8%), 29 had a normal outcome (29/73, 40%), and 23 were lost to follow-up (23/73, 31.5%). Seven out of 73 live-born children showed an adverse outcome (9.6%).Conclusions: Prenatal microarray in fetuses with isolated increased NT had a 5% (2/40) increased diagnostic yield compared to conventional karyotyping. Even with a normal microarray, fetuses with an isolated increased NT had a 28.8% risk of either pregnancy loss or an affected child.

CHROMOSOMAL DEFECTS IN INCREASED NUCHAL TRANSLUCENCY FETUS

Objectives: Determination of the prevalence of all chromosomal defects and its distribution in fetuses with increased nuchal translucency thickness. Methodology: This is a retrospective study among pregnant women indicated for amniocentesis by nuchal translucency above 2.5 mm and consent to the study. 2720 cases were included to the study during 6 years’ period from 2015 to 2020. All singleton pregnancies whose nuchal transluciency measurements were equal or over 2.5mm, were indicated for amniocentesis. Results: The study was consist of 2720 amniocentesis in which fetal nuchal transluciency was elevated. The median maternal age was 29.19 years old (range 17-46), and the median fetal crown-rump length was 66.9 mm (range 45– 84). The fetal karyotype was abnormal in 560 (20.6%) pregnancies. The popular chromosomal conditions were including trisomy 21(55%), trisomy 18 (11.2%), trisomy 13 (3.9%), 45, XO (2.7%). Chromosomal aberrations rate was 17.6% at maternal age of 30- 34, 34% and 50.0% at maternal age of 35- 39 and ≥ 40 respectively. Conclusion: In fetuses with increased nuchal translucency, more than a half of the chromosomal aberrations were trisomy 21 (55.0%). Structural rearrangements were 22.5%. Advanced maternal age (above 35) increases the risk of chromosomal aberrations.