Validation of fetal DNA fraction estimation and its application in noninvasive prenatal testing for aneuploidy detection in multiple pregnancies

• Published in: Prenatal diagnosis Vol. 39; no. 13; pp. 1273 - 1282
• Main Authors: Chen, Min, Jiang, Fuman, Guo, Yulai, Yan, Huanchen, Wang, Jiayan, Zhang, Longmei, Zeng, XiaoJing, Li, Sheng, Li, Yufan, Li, Nan, Zhang, Chunsheng, Zhu, Wentao, Du, Bole, Wang, Yang, Lan, Zhiheng, Luo, Xingcheng, Luo, Fei, Chen, Dunjin
• Format: Journal Article
• Language: English
• Published: England Wiley Subscription Services, Inc 01-12-2019
• Subjects: Aneuploidy; Chromosomes; Deoxyribonucleic acid; DNA; Fetuses; Gestational age; Patau's syndrome; Pregnancy; Sex; Test procedures; Trisomy; Twins; Y Chromosomes
• ISSN: 0197-3851; 1097-0223
• DOI: 10.1002/pd.5597

Objective
To analyze the fetal fraction, fetal sex, and chromosomal aneuploidy in multiple pregnancies using noninvasive prenatal testing (NIPT).
Method
A total of 362 pregnant women including 203 singleton pregnancies, 69 twins, and 90 higher‐order multiple pregnancies were recruited. Fetal fractions estimated by size ratio‐based and Y chromosome‐based approaches in singleton pregnancies with male fetus were used as source data to establish the model. The model was then applied to multiple pregnancies for fetal fraction estimation. By comparing the fetal fractions estimated by size ratio to those estimated by Y chromosome or autosomal chromosomes, fetal sex and chromosomal aneuploidy can be analyzed.
Results
The size ratio‐based approach has been well established in estimating fetal fractions for twin and higher‐order multiple pregnancies. Fetal fraction had a positive correlation with gestational age in twin and triplet pregnancies. Fetal sex was determined with accuracies of 98.6% (95% CI, 92.19%‐99.96%) in twins and 97.6% (95% CI, 91.76%‐99.71%) in triplet pregnancies. Four trisomy 21, one trisomy 18, and one trisomy 13 cases were detected by NIPT. Two trisomy 21 singleton pregnancies and one trisomy 21 twin pregnancy were confirmed by karyotyping.
Conclusion
Fetal sex and chromosomal aneuploidy in multiple pregnancies can be determined using NIPT.
What's already known
There is a lack of sufficient validation data of the test specificity and sensitivity in multiple pregnancies. Therefore, the application of NIPT for multiple pregnancies is limited.
What does this study add?
The fetal fraction estimation approach in singleton pregnancies has been extended to analyze fetal fraction, fetal sex, and chromosomal aneuploidy in multiple pregnancies.