Combined Application of Chromosome Karyotype and Microarray Analysis in Fetus With Increased Nuchal Translucency

Abstract Objective：To examine the risk of chromosomal abnormalities when the thickness of the nuchal translucency( NT ) is 2.5-2.9mm, to evaluate the cutoff value of NT for prenatal diagnosis, to explore the value of combined application of chromosome karyotype and microarray analysis, and to explore the relationship between NT ≥ 5.0mm and fetal prognosis. Methods：A total of 366 pregnant women who underwent prenatal diagnosis in Anhui Province Maternity and Child Health Hospital from January 2018 to August 2020 were collected, of which 241 cases had NT ≥ 2.5mm, 125 cases were elderly (35-38 years old) with NT < 2.5mm. We made grouping statistics on chromosome abnormalities,and compared the detection of chromosome abnormalities by karyotype and microarray analysis. At the same time, we followed up the fetuses with NT ≥ 5.0mm and analyzed their prognosis. Results: (1)Among the 366 cases with NT thickening,the detection rates of chromosome abnormalities by karyotype analysis and microarray analysis(CMA) were 13.39% (49/366) and 13.93% (51/366), respectively, and there was no significant difference (P>0.05), including 25 cases of trisomy 21, 5 cases of trisomy 18, 5 cases of Turner synthesis and 16 cases of other chromosome abnormalities. (2)We compared the effect of different NT value on the detection rate of pathogenic chromosomes, and found that the difference between NT ≥2.5mm and NT < 2.5mm was statistically significant(P<0.05). The detection rates of pathogenic chromosomal abnormalities in NT < 2.5mm group,2.5-2.9mm group, 3.0-3.4mm group,3.5-4.4mm group,4.5-5.4mm group and NT ≥ 5.5mm group were 0.8%(1/ 125), 11.63%(10/ 86), 17.81%(13/ 73), 20%(10/ 49), 47.62%(10/ 21) and 63.64%(7/ 11) respectively. (3)Our study found that different prenatal diagnostic indicators for abnormal chromosome detection rate difference was statistically significant(P<0.05). The detection rates of NT thickening alone and NT thickening combined with other abnormalities were 13.17%(22/ 167) and 35.14%(26/ 74) respectively(P<0.05). (4)Among 18 pregnant women with NT ≥ 5.0 mm, 9 fetuses were chromosomal abnormalities, and 9 fetuses survived healthily. Conclusions：When the NT value is 2.5-2.9mm, the incidence of fetal chromosome abnormality is significantly higher than that in the normal group. It is suggested that invasive prenatal diagnosis should be performed for pregnant women with NT ≥ 2.5mm. Chromosome karyotype analysis and CMA can complement each other, which is conducive to prenatal genetic counseling. The fetuses with NT thickening usually have good pregnancy outcomes when excluding fetal chromosome and prenatal ultrasound does not indicate any abnormalities.