| 【Objects】Investigate the clinical test value of CNV-seq technology in NT thickening fetus,and further analyze the genetic causes of NT thickening fetus.【Methods】Amniotic fluid samples of 92 fetuses with NT≥2.5mm were collected,and the genetic causes were analyzed and the pregnancy outcomes were followed up.【Results】1.For 92 cases of NT thickened fetal samples,the rate of chromosomal abnormalities detected by karyotype analysis was17.39%(16/92),including 8 cases of trisomy 21,5 cases of trisomy 18,2cases of chimerism and 1 case of changes of chromosome structure polymorphism.The detection rate of CNV-seq was 23.91%(22/92).Among them,13 cases of aneuploidy and 1 case of chimerism were consistent with the results of karyotype analysis,and in addition,1 case of chromosome large fragment deletion and 7 cases of chromosome microdeletion/microduplication were detected.2.According to NT value,karyotype analysis and CNV-seq detection rates of chromosomal abnormalities in fetuses with NT thickness of2.5mm-3.5mm,3.6mm-4.5mm and above 4.5mm were 11.86%(7/59)/15.25%(9/59),25.00%(6/24)/ 33.33%(8/24),33.33%(3/9)/ 55.56%(5/9),respectively.Trend analysis showed that for samples with different NT values,the detection rates of chromosomal abnormalities were significantly different in both karyotype analysis and CNV-seq(p < 0.05),and with the increase of NT value,the detection rates of karyotype analysis and CNV-seq were higher.3.When pregnant women with advanced age,adverse pregnancy history or other ultrasound abnormalities,the detection rate of karyotype analysis was 41.67%(10/24),and the detection rate of CNV-seq was54.17%(13/24);while in pregnant women without other adverse factors,the detection rate of karyotype analysis was only 8.82%(6/68),and the detection rate of CNV-seq was only 13.24%(9/68).No matter karyotype analysis or CNV-seq,the detection rate of chromosomal abnormalities in non isolated NT thickened fetuses was significantly higher than that in isolated NT thickened fetuses(p < 0.05),which indicated that if pregnant women with NT thickening had advanced age,adverse pregnancy history or other ultrasound abnormalities,the possibility of fetal chromosomal abnormalities was greatly increased.4.The results of karyotype analysis and CNV-seq were compared:(1)The detection rate of karyotype analysis was 17.39%(16/92),and the detection rate of CNV-seq was 23.91%(22/92),the detection rate of CNV-seq was higher than that of karyotype analysis in NT thickened fetus.(2)There were 14 cases of abnormal NT thickening detected by both karyotype analysis and CNV-seq,accounting for 15.22%(14/92).For the common chromosome aneuploidy abnormalities,the results of the two methods are basically the same.(3)8.70%(8/92)of samples were detected to be abnormal by CNV-seq but detected to be normal by karyotype analysis;and 2.17%(2/92)of samples were detected to be abnormal by karyotype analysis but detected to be normal by CNV-seq.Both karyotype analysis and CNV-seq have their unique advantages,but there are also some shortcomings and detection blind areas.(4)CNV-seq can detect chromosome microdeletions / microrepeats which can not be detected by karyotype analysis.【Conclusions】 Fetal NT thickening is closely related to chromosomal abnormalities,the higher the NT value,the higher the possibility of fetal chromosomal abnormalities,and the higher the risk of various chromosomal diseases.NT thickening can be used as an important screening index for fetal chromosomal abnormalities in early pregnancy.CNV-seq can improve the detection rate of pathogenic copy number variation.It is suggested that chromosome karyotype analysis and CNV-seq should be performed simultaneously in the diagnosis of genetic etiology of NT thickening fetus. |
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