Methods of detection and isolation of trophoblast cells from trans-cervical specimens – a historical overview

Trophoblast cells can be detected and isolated from the cervical epithelial cells obtained via various techniques of trans-cervical samples collection such as a mucus aspiration, endocervical lavage, or standard cervical brushing in the early first trimester, even from the 5 weeks’ gestation. Isolated fetal cells can be used in the early prediction of fetal sex, prenatal diagnostics of the most common aneuploidies, and any other genetic abnormalities. Nevertheless, the collection of trophoblastic cells has limited efficacy compared to currently used methods of detection of free fetal DNA in maternal circulation or other protocols of invasive prenatal diagnostics available at later stages of pregnancy. In the past years, trans-cervical cell samples were collected mainly in women before planned pregnancy termination. The early trophoblastic cells isolation from women in ongoing pregnancies opens new perspectives for further studies focused on the elucidation of pathophysiology of numerous pregnancy-related complications.

Estimation of cell-free fetal DNA fraction from maternal plasma based on linkage disequilibrium information

Cell-free fetal DNA fraction (FF) in maternal plasma is a key parameter affecting the performance of noninvasive prenatal testing (NIPT). Accurate quantitation of FF plays a pivotal role in these tests. However, there are few methods that could determine FF with high accuracy using shallow‐depth whole‐genome sequencing data. In this study, we hypothesized that the actual FF in maternal plasma should be proportional to the discrepancy rate between the observed genotypes and inferred genotypes based on the linkage disequilibrium rule in certain polymorphism sites. Based on this hypothesis, we developed a method named Linkage Disequilibrium information-based cell-free Fetal DNA Fraction (LDFF) to accurately quantify FF in maternal plasma. This method achieves a high performance and outperforms existing methods in the fetal DNA fraction estimation. As LDFF is a gender-independent method and developed on shallow-depth samples, it can be easily incorporated into routine NIPT test and may enhance the current NIPT performance.