Karyotype ana1ysis of small supernumerary marker chromosome in 20 486 samples for prenatal diagnosis / 中华围产医学杂志

ABSTRACT

Objective To investigate the detection rate,clinical indications and pregnancy outcomes of pregnancies with prenatally diagnosed small supernumerary marker chromosome (sSMC) to provide a theoretical foundation for prenatal diagnosis and genetic counseling of sSMC.Methods This study retrospectively analyzed the clinical data of 20541 cases who underwent prenatal diagnosis at the Prenatal Diagnostic Center in the Department of Obstetrics and Gynecology in Peking University First Hospital from January 2007 to May 2018.The detection rate,diagnostic indications and pregnancy outcomes of the cases with sSMC were analyzed after cell culture and karyotyping.Array comparative genomic hybridization (aCGH) was used to analyze the origin of fetal abnormal chromosome in some cases.Results Prenatal diagnostic samples of 20486 cases were successfully cultured,among which 20 (sSMC) were detected giving an detection rate of 0.98‰,while the figures in samples obtained through chorionic villus sampling,amniocentesis and umbilical cord blood sampling were 2.20 ‰ (2/910),0.74 ‰ (14/18824) and 5.32 ‰ (4/752),respectively.Twelve cases of mosaic karyotype were also found.In gravidas for prenatal diagnosis indicated by maternal or paternal chromosomal abnormality,fetal structural anomalies on ultrasonography,adverse pregnant history,advanced maternal age and high risk of Down's syndrome,the detection rates of sSMC were 10.42 ‰ (1/96),2.65 ‰ (4/1507),1.89 ‰ (5/2 643),0.83‰ (8/9 624) and 0.49‰ (2/4013),respectively.Eleven cases were further analyzed with aCGH,four of which showed pathogenic copy number variants involving 2q11.1-q12.1,2p12-p11.1 and 2q11.1-q12.1,7q 11.21-q 11.23 and 15q11.1-q 13.3 dup1ications and terminated the pregnancies.Seven cases carried nonpathogenic marker chromosomes,of which one terminated the pregnancy,while the other six continued to fullterm with uneventful outcomes until follow-ups.Conclusions sSMC is hard to detect in prenatal diagnosis,but maternal or paternal chromosomal abnormalities,fetal structural anomalies on ultrasonography and adverse pregnancy and childbirth history are strong indications.Cytogenetics and molecular diagnosis combined can clarify the character,origin and pathogenicity of sSMC,and is of great clinical importance in prenatal genetic counseling and maternal decision making.