Abstract
Prenatal screening for chromosomal abnormalities has two components i.e. prenatal screening (maternal serum screening and cell-free fetal DNA screening) and prenatal diagnosis (chorionic villus sampling, amniocentesis, and cordocentesis). Prenatal testing in the past decade is evolving towards non-invasive methods to determine the chromosome abnormality disorders in the fetus without incurring the risk of miscarriage. Conventional tools for prenatal screening included maternal age, maternal serum markers, ultrasound marker (nuchal thickness), and their combinations. With the increased risk of screening test patients were offered diagnostic tests (chorionic villus sampling, amniocentesis, and cordocentesis). After the availability of noninvasive prenatal tests for commercial use in 2011, a great marketing drive is there to establish it as a master tool for prenatal testing. However various society guidelines i.e. ACOG, RCOG, and ISUOG have clearly stated that cell-free fetal DNA based noninvasive prenatal tests is a screening test, not a diagnostic test. In the succeeding paragraph, we will review current trends in the field of cell-free fetal DNA noninvasive prenatal tests and the relevance of invasive testing in the context of noninvasive prenatal tests. Noninvasive prenatal tests does not entirely replace invasive prenatal testing procedures. Positive noninvasive prenatal tests findings must be confirmed by diagnostic tests based on an invasive sample source, mainly chorionic villus sampling or amniocentesis due to false positive and false negative reports of cell-free fetal DNA based tests. Continuing research and development efforts are focused on overriding noninvasive prenatal tests limitations. Recent studies show that procedure-associated risks in the case of prenatal invasive testing are very low as compared to previous studies. Prenatal invasive testing will remain as the backbone of prenatal diagnostic testing until the limitation of noninvasive prenatal tests is overcome.
Highlights
Prenatal testing for chromosomal abnormalities has undergone an evolution from traditional invasive methods (amniocentesis or chorionic villus sampling (CVS)) to non-invasive methods i.e. maternal age, maternal serum screening, ultrasound, and cell-free fetal DNA noninvasive prenatal tests (NIPT)
Even with high detection rates of >99% and low false-positive rates, it is important to emphasize that cell-free fetal DNA (cffDNA) NIPT remains a screening test as per various society guidelines and those women with a high-risk result require invasive testing to confirm the findings of prenatal chromosome abnormality
If cffDNA-based tests indicate a trisomy, confirmatory testing in the form of invasive testing is needed before offering a conclusion
Summary
Prenatal testing for chromosomal abnormalities has undergone an evolution from traditional invasive methods (amniocentesis or chorionic villus sampling (CVS)) to non-invasive methods i.e. maternal age, maternal serum screening, ultrasound, and cell-free fetal DNA (cffDNA) noninvasive prenatal tests (NIPT). Relevance of Invasive Testing in Era of Non-Invasive Testing for Prenatal Chromosomal Abnormalities. Gynecol Obstet Reprod Med. 2020;Articles in Press ported in 1877 but its use for genetic prenatal diagnosis started in the 1970s for high-risk pregnancies [1,2]. The introduction of ultrasound imaging guidance in the procedure led to a marked safety profile of CVS and amniocentesis [4]. Due to a 1% to 2% risk of miscarriage associated with invasive procedure and advancement in next-generation sequencing (NGS) leads to the development of non-invasive prenatal testing based on maternal blood. The performance of various serum screening tests for trisomy 21 with a 5% false-positive rate is shown in table I [5]
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