Clinical Application Of Non-invasive Prenatal Testing Based On Cell-free Fetal DNA Of Pregnant Women In Twin Pregnancies

BackgroundWith the development of assisted reproductive technology,the increase in maternal age and the use of ovulation-inducing drugs,The number of multiple births has risen dramatically to an average of 3%.Since the incidence of fetal chromosomal abnormalities is significantly higher in twin pregnancies than in singleton,prenatal testing for twin pregnancies can not be ignored.Traditional screening using maternal serum markers,NT,and maternal age for twin pregnancies has a lower sensitivity and higher FPR than for singleton.As for invasive prenatal diagnosis which has been considered to be gold stander for fetal aneuploidies has a higher rate of miscarriage and preterm delivery in twin pregnancies than that of singleton.Noninvasive prenatal testing(NIPT)using cell-free DNA(cfDNA)in maternal peripheral blood has opened the door to early,accurate,and safe prenatal testing for fetal chromosomal aneuploidy,which has been widely used in singleton,but there are fewer relevant clinical studies in twin pregnancies,and still some limitations,too.Objective1.To investigate health professionals’ opinions toward offering noninvasive prenatal testing(NIPT)as first-tier screening test regardless of pregnant women’s risk,and toward a potential broader range of disorders.have a better understanding of the attitudes,awareness and of NIPT among pregnant women and to improve in key areas such as NIPT-related knowledge dissemination and the regulation of pre-test counseling.2.To raise awareness of the current status of aneuploidy screening of twin pregnancies in domestic and abroad,to identify the value and potential risks of NIPT in aneuploidy screening of twin pregnancies.3.To evaluate the performance of NIPT with cffDNA enrichment,and to provide a provide a reference for future large-scale studies and further clinical applications of NIPT.Method1.Designing a questionnaire in accordance with relevant technical standards,and conducting a questionnaire survey among the relevant practitioners of various levels of medical units,prenatal screening and diagnostic centres in Guangdong Province.2.Retrieval,screening,evaluation and eventually including of 17 high-quality clinical studies for meta-analysis of publicly available studies using fetal free DNA screening in pregnant women’s plasma for aneuploidy in twin pregnancies by March 2020.3.Review the analysis of the testing of non-invasive prenatal screening of peripheral blood samples from pregnant women with twin pregnancies by the Medical Genetic Center of the Guangdong Women and Children Hospital from 2015 to 2019 by semiconductor sequencing and evaluate its effectiveness.Results1.A total of 615 questionnaires were collected,of which 572 were valid and 93.01% were collected,of which 213 were completed by medical personnel and 359 by pregnant women.93.62% of the respondents believed that NIPT should be provided to pregnant women with twin pregnancies and the vast majority of respondents believed that NIPT for twin pregnancies is a high risk.Prenatal screening practitioners were not sufficiently knowledgeable about NIPT in twin pregnancies,with prenatal diagnosticians and laboratory staff having higher knowledge of NIPT than obstetricians(p=0.000);only 6.50% of clinicians considered personal genetic counseling for twin pregnancies to be comprehensive and detailed.Pregnant women with two pregnancies are more willing to accept NIPT and are more likely to refuse prenatal diagnosis than those with a single pregnancy.2.This meta-analysis involved a total of 9754 cases of twin pregnancies,of which T21 accounted for 1.27%,T18 for 0.5% and T13 for 0.22%.The present shows that the sensitivity of NIPT screening for T21,T18 and T13 in twin pregnancy was 98%,89% and 99%,respectively,with a specificity of 100%,NIPT has high performance sensitivity and specificity for detecting T21 in twin pregnancies,and is similar was similar to that of studies in singleton pregnancies,with slightly higher specificity than sensitivity.3.The detection rate,sensitivity,specificity,PPV,FPR of fetal chromosomal aneuploidy was 100%,100%,99.73%,91.67% and 0.27% for NIPT in twin pregnancies from 11 to 30 weeks’ gestation by semiconductor sequencing,the average FF increased from 13.39% to 18.24%,while the failure rate decreased significantly(P<0.05).Conclusion1.The key to the rational and correct application of NIPT lies in how clinicians interpret and how pregnant women understand NIPT,but clinicians and pregnant women with two pregnancies have little or no understanding of NIPT.2.In twin pregnancies,the performance of NIPT is similar to that reported in singleton pregnancy and is superior to that of the first-trimester combined test or second-trimester biochemical testing.Due to the small number of T13 cases,an accurate assessment cannot yet be given.3.This study demonstrates that it is feasible to increase FF by selectively enriching short cfDNA fragments.Although The high accuracy of chromosomal aneuploidy detection in twin pregnancies,the number of affected fetuses cannot be determined,and the results must be confirmed by invasive prenatal diagnosis.