The prenatal diagnostic results of unexpected findings after non-invasive prenatal testing
Chang Jiazhen , Zhou Xiya , Qi Qingwei , et al
1. Medical Research Center, Chinese Academy of Medical Sciences, Peking Union Medical College, PekingUnion Medical College Hospital, Beijing 100730, China; 2. Obstetric Center, Chinese Academy of MedicalSciences, Peking Union Medical College, Peking Union Medical College Hospital, Beijing 100730, China
【Abstract】 Objective To analyze the prenatal diagnostic results of chromosomal aneuploidy high risk
cases except trisomy 21,18,13 after non-invasive prenatal testing (NIPT), so as to provide evidence for clinical
management for these unexpected fifindings. Methods The 25 334 results of NIPT performed from April1, 2016 to September 30, 2019 in Peking Union Medical College Hospital were analyzed retrospectively.Genetic counselling was provided for women with NIPT high risk results, and amniocentesis andkaryotyping were performed after informed consent. Fluorescence in situ hybridization (FISH) and/or chromosomal microarray (CMA) analysis were performed meanwhile. For those cases in which theprenatal diagnostic results were inconsistent with NIPT results, copy number variation sequencing (CNVseq) were done for the maternal white blood cell, in order to assure if there was maternal disturbanceof chromosomal abnormalities or copy number variations (CNV). Results There were 199 unexpectedfifindings in all the 25 334 NIPT (0.79%, 199/25 334), with 141 (0.56%, 141/25 334) sex chromosomal
aneuploidies (SCAs) high risk results and 58 (0.23%, 58/25 334) rare autosomal trisomies (RATs) highrisk cases. 132 SCAs high risk cases received prenatal diagnosis, among which 44 cases had consistent
results with NIPT, with a overall positive predict value (PPV) of 33.3%. The PPV for chrX-, chrX+,
chrX+(Y), chrX-(Y) and chrY+ were 14.29%, 36.36%, 58.62%, 0.00% and 100.00%, respectively. 49
RATs high risk cases received prenatal diagnosis, and the most common RATs high risk happened with
chromosome 7 (seven cases). When the prenatal diagnostic results were discordant with NIPT fifindings,
25.0% (22/88) of the SCAs were due to maternal reasons, and 8.6% (3/35) of the RATs were due to
maternal reasons. Conclusions The unexpected fifindings after NIPT wwre not rare, with different PPV
for different chromosomes. Fetus-placenta chromosomal discordance and maternal reasons might be the
main reasons of discordant results of NIPT and prenatal diagnosis. Invasive prenatal diagnosis should berecommended for the unexpected fifindings, and more attention should be paid for mosaic trisomies andpregnancy outcomes.
2020, Vol. 8 
