Re: Low‐molecular‐weight heparin associated with reduced fetal fraction and subsequent false‐ negative cell‐free DNA test result for trisomy 21

Cell-free DNA (cfDNA) screening for fetal trisomy 21, 18, and 13 is now widely used in clinical practice. However, false-positives and false-negatives did occur1,2. Actually, the majority of fetal cfDNA in maternal blood is from placental trophoblasts.