Nonreportable rates and cell‐free DNA profiles in noninvasive prenatal testing among women with heparin treatment

Abstract Objective To evaluate the “nonreportable” rate in patients treated with heparin and to determine the effect of heparin on the results of noninvasive prenatal testing (NIPT). Method This was a single‐center retrospective study of NIPT. The “nonreportable” rate of NIPT was evaluated according to presence or absence of heparin treatment. After excluding true‐positive cases, a matched cohort study evaluating Z‐scores, GC bias, and cell‐free DNA (cfDNA) profiles was performed to investigate the effect of heparin on NIPT results. Results Overall, 2651 singleton pregnancies with available clinical information were evaluated; 23 mothers were treated with heparin. The nonreportable rate was much higher among patients treated with heparin than among those who were not (8.70% vs 0.15%). In the matched cohort study, the Z‐scores for chromosomes 13, 18, and 21, and GC bias were significantly higher in the heparin group than in the matched control group. Based on cfDNA library electrophoresis data, the proportion of short‐sized cfDNA was higher in the heparin group. Conclusion Heparin use increased the nonreportable rate of NIPT results by borderline Z‐scores, possibly caused by the increased proportions of shorter and GC‐rich cfDNA fragments. This information will be helpful for prenatal genetic counseling for patients requiring heparin treatment.