| Part One Cytogenetic analysis of 3387 umbilical cord blood in pregnant women at high risk for chromosomal abnormalitiesObjective:1.To explore the detection rates and distribution of abnormal karyotypes among different indications for prenatal genetic cordocentesis and analyze the significance of chromosome karyotype analysis of umbilical cord blood culture in the middle and late pregnancy.2.Explore the choice of genetic testing methods for pregnancies with isolated soft marker.3.Analysis of the outcome and prognosis of foetuses with sex chromosome mosaicism.4.Clinical analysis of foetal chromosome polymorphism in umbilical cord blood culture.Methods: This was a retrospective study.A total of 3387 pregnant women at high risk for foetal chromosomal abnormality underwent cordocentesis for rapid prenatal karyotyping in the Department of Reproductive Genetic Family of Hebei General Hospital between January 2011 and December 2018.The indication distribution and incidence of chromosomal abnormalities was analyzed,and further follow-up were performed to explore the pregnancy outcome and progress of foetuses with Chromosome polymorphisms or sex chromosome mosaicism.Results:1.Detection rates and distribution of abnormal karyotypes among different indications for prenatal genetic cordocentesisOut of 3387 samples obtained during invasive sampling procedures under ultrasound guidance,a total of 182 cases of abnormal karyotypes were detected,the incidence of chromosomal abnormalities was 5.37%.Of the 182 cases,119(65.38%)had chromosomal numerical abnormalities;trisomy 21 was the most noted of the chromosomal numerical abnormalities,while chromosomal inversion was the most common of the chromosomal structural abnormalities,accounting for 10.44%,and most of the cases were pericentric inversions on chromosome 9;There were 19 cases of mosaicism diagnosed prenatally in cord blood culture,involving 16 cases of sex chromosome mosaicism.Among all indications for prenatal genetic cordocentesis,ultrasound soft markers accounted for 73.16%;but the lowest chromosomal abnormalities rate of 2.02% was observed in the ultrasound soft markers group,while the rate was 11.17% in the ultrasonographic structural abnormal findings group,19.30% in the advanced maternal age group,33.33% in the either mother or father with chromosomal abnormality group,46.97% in the NIPT-positive group and 44.23% in the karyotype confirmation after amniocentesis group.Autosomal aneuploidy(trisomy 21,18,and 13)mainly occurred in the NIPT-positive and ultrasonographic structural abnormal findings groups.Sex chromosomal abnormalities mainly occurred in the NIPT-positive group,while mosaics mainly occurred in the karyotype confirmation after amniocentesis group.Chromosomal deletion,duplication,addition and derivative chromosome mainly occurred in the ultrasonographic structural abnormal findings group,while chromosomal translocation and inversion mainly occurred in the ultrasound soft marker group.2.Distribution of sex chromosome mosaicism and pregnancy outcomeFurther follow-up indicated that 13 pregnant women chose to terminate their pregnancies,in which a foetus with karyotype 46,X,i(Y)(q10)[20]/45,X[6] showed unclear genitals.Three pregnant women elected to continue pregnancy with foetuses with lower proportion sex chromosome mosaicism and delivered healthy neonates.3.Karyotype confirmation for abnormal karyotypes in amniotic fluid cell cultureThere were 52 cases that underwent genetic cordocentesis due to abnormal karyotypes in amniotic fluid cell culture,and 29 cases were verified to be normal karyotypes in foetal blood culture.Those pregnant women continued pregnancy and delivered healthy neonates.23 cases were confirmed to be abnormal karyotypes in foetal blood karyotyping,of which 10 cases were mosaics.4.Distribution of chromosome polymorphism and pregnancy outcomeOut of 80 cases of chromosome polymorphism,13 cases were lost to follow-up;six pregnant women chose pregnancy termination due to pathological ultrasound findings.Among the 61 cases with the continuation of the pregnancy,one foetus suffered severe neonatal asphyxia after birth,one foetus had mild varus pedis and a foetus died of postnatal pneumonia complicated by encephalitis.Conclusions:1.NIPT can be taken as an alternative for pregnancy with isolated soft marker in the setting of no other risk factor for aneuploidy,and the patients should be informed the limitations of the application of NIPT.2.NIPT should not be recommended as the first-tier screening for chromosomal aberration for pregnancies at advanced maternal age,but it can be taken as an alternative for pregnancy with invasive prenatal diagnosis contraindications.3.Diagnostic testing for karyotype and chromosomal microarray analysis should be offered if a structural abnormality is found by ultrasound.4.Mosaicism found in amniotic fluid cell culture requires further cordocentesis for karyotype confirmation,and the continuation of the pregnancy is safe when a normal karyotype is identified in foetal blood culture.5.The prognosis is good for foetuses with a lower proportion sex chromosome mosaicism.6.Further genetic testing and parental karyotype analysis were needed for foetal Chromosome polymorphisms.Part Two Application of chromosome microarray analysis in prenatalgenetic diagnosisObjective: To explore the application of genome-wide high resolution chromosomal microarray analysis(CMA)in prenatal diagnosis,and analysis the difference of karyotype analysis and CMA in pregnancies with indications for prenatal genetic diagnosis.Methods: Karyotype analysis and chromosome microarray analysis of amniotic fluid or cord blood were performed on 706 high-risk pregnancies with indications for genetic amniocentesis or cordocentesis in the Department of Reproductive Genetic Family of Hebei General Hospital.The detection rates and distributions of abnormal karyotypes were observed in a variety of indications for prenatal genetic diagnosis.The incidence of chromosomal abnormalities and CNV were analyzed in pregnant women with different indications for invasive diagnostic paracentesis.Results: Out of the 706 cases performed karyotype analysis and CMA,chromosome abnormality was found in 81 cases(11.47%).Among all indications for prenatal genetic diagnosis,the common one is ultrasound soft markers accounted for 36.54%;Of the 81 cases,46 cases(56.79%)had chromosomal numerical abnormality and 35 cases(43.21%).Trisomy 21 was the most noted in the chromosomal numerical abnormalities,whilst chromosomal translocation was the most noted in the chromosomal structural abnormalities.CNV were detected in 122 fetuses accounted for 17.28%,increased 5.81% in chromosomal aberration detection.Among the pregnancies performed genetic amniocentesis or cordocentesis with different indications,the detection rate of chromosomal aberration in CMA is higher than that in karyotype analysis except pregnancy women in either mother or father with chromosome abnormality group.Among 622 cases with normal karyotype in G-banded karyotyping,63(10.13%)cases with chromosomal microdeletions and microduplications were detected.Conclusions: CMA plays an important role in prenatal diagnosis.Chromosome karyotype analysis combined with CMA in prenatal genetic diagnosis can improve the detection rate of chromosomal aberration.Part Three Application of gene sequencing in prenatal genetic diagnosisObjective: To study the clinical application of gene sequencing in prenatal genetic diagnosis.Methods: Genetic patterns analysis and next-generation sequencing was performed for a family with suspected hereditary spastic paraplegia to identify the pathogenic mutations and clarify the diagnosis.The pregnant woman was performed genetic amniocentesis,amnio fluid was obtained to extract DNA,and Sanger sequencing was performed for genetic testing.Results: Next-generation sequencing for the proband revealed the mutations c.22C?T(p.R8X)(origin from father)and c.341G?C(p.G114A)(origin from father)in IBA57 gene,the same mutations were found in sequencing of his brother.The proband diagnosed with spastic paraplegia type 74 based on clinical phenotype,genotype and inheritance patterns.The G-band karyotypes of foetuses revealed normal karyotype.One foetus carried the mutation c.341G?C,while no mutation was not found in another foetus.Delivery occurred at 34 weeks of gestation.Further follow-up for two more years revealed that there was no any developmental disorder in the two foetuses.Conclusions: ABCG5 gene mutation is an important etiological factor for hereditary spastic paraplegia,and gene sequencing plays an important role in precision medicine and prenatal genetic diagnosis. |
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