Fetal nucleated cells in maternal peripheral blood after delivery.

OBJECTIVE

The purpose of this study was to determine the frequency of fetal nucleated cells and their serial changes in maternal peripheral blood after delivery.

STUDY DESIGN

A total of 135 blood samples were investigated by means of fluorescence in situ hybridization by observing cells with Y chromosomes. Polymerase chain reaction amplifying two different Y-specific fragments were also carried out for genomic deoxyribonucleic acid from the same samples.

RESULTS

The mean frequency of the Y-positive cells detected by fluorescence in situ hybridization in mothers who gave birth to male children was about 1 in 17,500 1 day after delivery. The frequency of these cells decreased with time, dropping below detectable levels 3 months after delivery. The frequency estimated by polymerase chain reaction experiments was significant and positively correlated with those found by fluorescence in situ hybridization.

CONCLUSION

Fetal nucleated cells in maternal peripheral blood decrease in frequency with time after delivery. These cells disappear from maternal circulation 3 months after delivery in most, if not all, mothers.