When Is Non-Invasive Prenatal Testing Reliable in Pregnancies with Vanishing Twin? - A Review of Case Reports

Background: Fetal demise can complicate aneuploidy screening in a multi fetal pregnancy. The cell-free DNA (CF-DNA) from a non-viable conception may lead to be discordant with the viable fetuses. The Aim of study was to review the waiting period, follow-on single fetal demise in a twin gestation before performing NIPT. Materials and Methods: In this review articlewe searched through online database with keywords: ((NIPT) (non-invasive prenatal screening testing) (cell-free DNA) (vanishing twin) (co-twin demise)), including: CINAHL, Cochrane, Database of Abstracts of Reviews of Effects (DARE), PubMed, and Medical Library. For English literature between 2011 and 2020 which included duration between vanishing twin or reduction and NIPT false results. Results: 201 studies across the eight scientific web sites were detected. 178 excluded for duplication or being irrelevant. 29 studies were fully read. 4 case series, met the criteria for systematic review. The finding suggested the NIPT screening test can be falsely-positive several weeks after vanishing twins although live fetus is normal. Therefore, duration in which placenta can release CF-DNA of vanished twin is unknown. In addition, several weeks after reduction the fetal CF-DNA increases and then decreases, thus CF-DNA analyzing in multi-fetal pregnancies with reduction can be challenging as well. Conclusion: In pregnancies with vanishing twin or reduction, evaluating NIPT results is more complex than single fetal pregnancy. According to studies, after a fetal demise, the cytotrophoblast continues to release to the CF-DNA in the maternal circulation for a variable time, which may cause a false-positive result if the demised twin is aneuploidy.