Effect of labor on postpartum clearance of cell-free fetal DNA from the maternal circulation.

OBJECTIVE

The aim of this study was to compare the effect of mode of delivery on the postpartum clearance of cell-free fetal (cff) DNA.

METHODS

Women who gave birth to a single-term male infant by any mode of delivery had blood collected on three occasions: within 3 h of birth, on day 1-2 postpartum and at 2 weeks postpartum. The SRY sequence was used as a marker of cff DNA, and was detected using conventional PCR.

RESULTS

Eighty-seven women were included in the study. There were 28 women in the elective caesarean section group and 59 in the labor group. Cell-free fetal DNA was detected in 38/87 (44%) of women within 3 h of birth. There was a significant difference between the group that labored and the group that did not (54 vs 21%, p = 0.003). Twelve percent of women who labored had persistent cff DNA on day 1-2 postpartum, compared with none of the women who delivered without labor. No woman had DNA that persisted up to 2 weeks postpartum.

CONCLUSION

The presence of labor increases the rate of detectable DNA in women within 3 h of birth and on day 1-2 postpartum. Postpartum clearance was completed by 2 weeks in all women tested regardless of mode of delivery.