Objectives: On the basis of reports of maternal cells being detected in the umbilical cord blood of newborn infants, we tested the hypothesis that maternal cells can migrate out of the circulation into newborn tissues.
Study design: We studied autopsy material from 4 newborn infants who never received a blood transfusion and died during the first week of life. The study subjects' diagnoses were trisomy 21 with nonimmune hydrops, 46, XY, 4q+ with multiple congenital anomalies, Potter syndrome, and congenital ichthyosis. Fluorescence in situ hybridization analysis with X and Y chromosome-specific probes was performed on sections of paraffin-embedded tissue, including liver, spleen, thymus, thyroid, and skin.
Results: Female cells, as defined by the presence of intact nuclei with two X chromosome signals, were detected in multiple tissue types from all 4 male neonates. The number of female cells varied from 3 to 45 per slide.
Conclusions: Maternal cells enter the fetal circulation and are capable of migration to fetal and neonatal organs. This is of importance with regard to potential consequences of umbilical cord blood transplantation and postnatal development of autoimmune disease.