Conclusions
Continuous detection of a significant risk of fetal trisomy after fetal reduction indicated that residual cfDNA remained in maternal plasma for around 12 to 22 weeks after fetal demise. The persistent detection of residual cfDNA of the demised co-twin has a long-lasting influence on the results of NIPT. It should be cautious about providing NIPT in pregnancies with a risk of fetal demise.