Study On Interventional Prenatal Diagnosis And Pregnancy Outcome Of Fetuses With NT Thickening

Objectives:To investigate the interventional prenatal diagnosis,fetal system ultrasonography,pregnancy outcome,postnatal growth and development of fetus with thickened nuchal translucency（NT）in early pregnancy,so as to provide a reference for clinical work.Methods:A total of 27,529 pregnant women who underwent NT ultrasound screening at11-13⁺⁶weeks of gestation in Fujian maternal and Child Health Hospital from May2015 to December 2019 were collected,and 625 cases of fetal NT thickening（NT≥2.5 mm）were detected.310 pregnant women who visited the prenatal diagnosis center and received prenatal diagnosis（karyotype and SNP array analysis）were finally included in the study.According to the thickness of NT,they were divided into four groups,Group A（NT 2.5-2.9 mm）,Group B（NT 3.0-3.4 mm）,Group C（NT 3.5-4.9 mm）and Group D（NT≥5.0 mm）.According to whether it is combined with other ultrasound soft indicators or structural abnormalities,divided into simple NT thickening group and combined with other ultrasound abnormalities group.The relationship between NT thickening and interventional prenatal diagnosis,fetal system ultrasonography and pregnancy outcome were analyzed.Using the case-control method,238 cases of infants with NT thickening and survival were selected as the observation group,and 238 infants with normal development during the fetal period were randomly selected as the control group according to the ratio of 1:1.The physical growth and development Z score and neuropsychological development screening were compared between the two groups.Chi-square test,Fisher exact test and t test were conducted with SPSS21.0statistical software.Results:1.There were 27529 pregnant women with NT screening at 11-13⁺⁶weeks of gestation,625 cases of fetal NT thickening（NT≥2.5 mm）were detected,and the incidence of NT thickening was 2.27%.2.The age distribution of 310 pregnant women included in the study ranged from 21 to 44 years,with an average age of（31.28±4.62）years.The thickness of NT ranged from 2.5 mm to 15.0 mm,with a median of 3.0 mm.Divided into 4groups according to NT value,Group A,NT 2.5-2.9 mm 132 cases（42.58%）,Group B,NT 3.0-3.4 mm 93 cases（30.00%）,Group C,NT 3.5-4.9 mm 64 Cases（20.65%）,Group D,NT≥5.0 mm 21 cases（6.77%）.3.A total of 33 cases（10.64%,33/310）were detected by chromosomal karyotype and SNP array analysis.24 cases（7.74%,24/310）were detected by karyotype analysis,including 22 cases of aneuploidy and 2 cases of chromosomal structure abnormality.10 cases of benign variation were detected,including 6 cases of chromosome inversion and 4 cases of polymorphism.SNP array detected 38cases of CNV（12.26%,38/310）,of which 21 cases of aneuploidy and 2 cases of chromosomal structure abnormalities were consistent with the karyotype analysis.In the other 15 cases of CNV,5 cases were pathogenic and 4 cases possibly pathogenic.Improve the positive diagnosis rate（2.90%,9/310）.4.According to the thickness of NT,7 cases（5.30%,7/132）were detected in Group A,7 cases（7.53%,7/93）in Group B,9 cases（14.06%,9/64）in Group C,and 10 cases（47.62%,10/21）in Group D.With the increase of NT thickness,the incidence of chromosomal abnormalities increased,and the difference was statistically significant（P<0.05）.According to the ultrasound indicators,19 cases（7.17%,19/265）of chromosomal abnormalities were detected in simple NT thickening group,and 14 cases（31.11%,14/45）were detected in other ultrasound abnormalities group,the difference between the two groups was statistically significant（P<0.05）.5.Excluding 23 cases of induced labor,2 cases of abortion and 35 cases of refusal to follow-up,250 cases of fetals were examined by system ultrasonography.A total of 22 cases（8.80%,22/250）of structural abnormalities were detected.There were 6 cases（5.26%,6/114）with abnormal structure in Group A,5 cases（6.76%,5/74）in Group B,8 cases（15.09%,8/53）in Group C and 3 cases（33.33%,3/9）in Group D.The incidence of abnormal fetal structure increased with the increase of NT thickness,and the difference was statistically significant（P<0.05）.6.275 cases of pregnancy outcomes were followed up,with a follow-up rate of 88.71%（275/310）.There were 30 cases of induced labor（10.91%,30/275）,2cases of spontaneous abortion（0.73%,2/275）and 243 cases of live birth（88.36%,243/275）.The incidence of adverse pregnancy outcomes（including structural deformity,induced labor and abortion）in each group was 12.71%,16.25%,25.42%and 66.67%respectively.The higher the NT value,the higher the incidence of adverse pregnancy outcomes,the difference was statistically significant（P<0.05）.7.The pregnancy outcome of chromosomal abnormalities.Among 22 cases with aneuploidy,21 cases chose to induce labor,only 1 case of chimera chose to continue full-term delivery.2 cases of cat’s cry syndrome were induced labor,6cases of chromosomal inversion and 4 cases of chromosomal polymorphism were full-term labor.Among the 15 cases of CNV,3 out of 9 cases of CNV were induced labor and 6 of them survived.1 case of benign CNV and 5 cases of VOUS were full-term delivery and survived.8.Among the infants in the observation group who were followed up,some of the infants with chromosomal abnormalities or structural abnormalities indicated by systematic ultrasound showed slow growth and development or abnormal neuropsychological screening after birth.However,there was no significant difference in the overall Z score of physical growth and development and neuropsychological screening between the observation group and the control group（P>0.05）.Conclusions:1.The incidence of NT thickening was 2.27%,and the incidence of chromosomal abnormalities was 10.64%.With the increase of NT thickness,the incidence of chromosomal abnormalities increased.The incidence of chromosomal abnormalities increased significantly when NT thickening combined with other ultrasound abnormalities.SNP array analysis further detected chromosome microduplication/microdeletion,which increased the diagnosis rate of chromosome abnormalities by 2.90%.2.It is recommended to use NT 2.5mm as the cut-off value for interventional prenatal diagnosis.If it is set as 3.0mm,2.26%of fetuses with chromosomal abnormalities will be missed;if it is set as 3.5mm,4.52%will be missed.3.With the increase of NT thickness,the incidence of fetal ultrasound structural abnormalities and adverse pregnancy outcomes increased.The most common structural abnormalities is cardiac dysplasia.Attention should be paid to fetal system ultrasonography in the second trimester.Most fetuses without ultrasound structural abnormalities grow well.