Fetal DNA clearance from maternal plasma is impaired in preeclampsia.

BACKGROUND Increased fetal DNA in maternal plasma/serum has been reported in pregnancies complicated by preeclampsia. We hypothesized that impaired clearance of fetal DNA might contribute, at least in part, to the above-mentioned phenomenon. METHODS We studied 7 preeclamptic and 10 control pregnant women. All had male fetuses. Serial blood samples were obtained from before delivery to 6 h postpartum. Male fetal DNA in maternal plasma was measured by real-time quantitative PCR for the SRY gene on the Y chromosome. RESULTS The median fetal DNA concentrations before delivery were significantly higher in the preeclamptic women than in the controls (521 vs 227 genome-equivalents/mL for preeclamptic and control women, respectively; Mann-Whitney rank-sum test, P = 0.017). The median fetal DNA concentrations at 6 h after delivery were also significantly different between the two groups (208 vs 0 genome-equivalents/mL for preeclamptic and control women, respectively; Mann-Whitney rank-sum test, P = 0.002). A first-order clearance model was found to best describe the kinetics of maternal plasma fetal DNA clearance. Moreover, we observed a significant difference in the median apparent clearance half-lives of fetal DNA between the preeclamptic women (114 min) and controls (28 min; Mann-Whitney rank-sum test, P = 0.007). CONCLUSIONS This study represents the first documentation of impaired fetal DNA clearance from maternal plasma in preeclampsia. Such an abnormality in circulating DNA clearance may also be present in other medical conditions associated with quantitative aberrations in circulating DNA concentrations.