Clinical Utility Of Non-invasive Prenatal Testing In Multiple Pregnancies

Objective To evaluate the performance of non-invasive prenatal testing of trisomy 13,trisomy 18 and trisomy 21 and the feasibility of clinical utility in multiple pregnancies.Method 1.The twin and triple or higher-order pregnant women consulted in the Department of Prenatal Diagnosis and Fetal Medicine of The Third Affiliated Hospital of Guangzhou Medical University were recruited from December 2017 to April 2019.Besides,some single pregnancies were also collected for validating the experimental approach.2.The gestational week of enrolled pregnant women must be more than 9 weeks and the cases that accepted allogeneic blood transfusion,transplant surgery,cell therapy,or immunotherapy within one year were excluded otherwise it may affected the sequencing results.3.A consent of non-invasive prenatal testing was offered to the all pregnant women recruited in this study and the signature was needed.4.Some detailed information such as name,date of birth,age,phone number,last menstrual period,times of gestation and production,conception of pregnancy this time,gestational week,the adverse pregnancy history and ultrasound examination.5.We used the QIAamp Circulating Nucleic Acid Kit(Qiagen,Hilden,Germany)to extract the fetal free-DNA and the Tru Seq Nano DNA Library Prep Kit(Illumina,Hayward,CA,USA)to prepare the DNA library.The process of sequencing was performed on the platform of Illumina.6.We verified the NIPT result with karyotype or chromosomal microarray analysis or follow-up study.Result 1.A total of 69 twin pregnancies and 90 triple or higher-order pregnancies were recruited in this study.Besides,203 singleton cases for validating the experimental approach were also recruited.The maternal age was between 18 and 48 years old and average age was 31 years old.There were 33(33/69,47.8%)twin pregnancy cases and 85(85/85,100%)triplet cases underwent NIPT before 20 gestational week.2.There were 44(63.8%)monochorionic and 20(29%)dichorionic pregnancies in twin pregnancies.Besides,there were 8(9.4%)monochorionic,31(35.5%)dichorionic and 45(52.9%)Trichorionic pregnancies in triplet.The most common conception in multiple pregnancies was by human assisted reproductive technology.3.The fetal sex prediction accuracy in twin and triple pregnancies were 98.6% and 97.6%,respectively.4.Three cases were detected positive with trisomy in all multiple pregnancies,including one case with trisomy 21/trisomy 21,one case with trisomy21/normal,and one case with trisomy7/normal.5.There was no false positive cases and false negative cases in this study.The detected rate in twin pregnancies using NIPT was 100%,and the specificity and negative predictive value in triple or higher-order pregnancies with NIPT was both 100%.Conclusion 1.The detected rate of NIPT used in multiple pregnancies for fetal aneuploidies detecting is high,and the application of NIPT used in multiple pregnancies in clinic is feasible.2.Usually,NIPT can be performed at as early as 12 weeks and with the characteristic of non-invasive.Comparing with invasive prenatal diagnostic method such as amniocentesis or chorionic villus sampling which may cause a miscarriage,NIPT is more acceptable for pregnant women.3.The limitation of NIPT used in multiple pregnancies is that when only one fetus affected with aneuploidies,it couldn't distinguish which one is the affected one and further an invasive procedure is needed.