Foreign fetal cells persist in the maternal circulation.

Objective: To determine whether allogenic fetal cells resulting from donor egg pregnancies persist in maternal circulation.

Design: Nested polymerase chain reaction (PCR) amplification of the DYS14 sequence, a region of the Y chromosome, from DNA purified from peripheral blood cells.

Setting: Academic medical center.

Patient(s): Healthy 18-60-year-old women who have had donor egg pregnancies resulting in a male offspring (n = 11) or, as a control, female offspring (n = 8), at least 1 year previously and without any other source for male cells in their peripheral blood or a healthy male.

Intervention(s): None.

Main Outcome Measure(s): Detection of DYS14 sequence by nested PCR.

Result(s): DYS14 was detected in 5/11 (45%) of women who had donor egg pregnancies resulting in a male offspring, but in 0/8 (0) of women who had donor egg pregnancies resulting in a female offspring. The longest interval between delivery of a male offspring and detection of the DYS14 gene was 9 years.

Conclusion(s): Unmatched, allogenic fetal cells from donor egg pregnancies are able to persist in the circulation of healthy women for at least 9 years after delivery. This implies a novel mechanism by which immunologic detection is avoided by these cells and may impact on how they may be used for regenerative and transplant medicine.