Purpose: To determine the frequency of maternal-fetal hemorrhage at or
above 1 mu l of maternal whole blood. Methods: Seventy-three mothers
whose red blood cells bore an Rh antigen (Rh D, Rh c, Rh E) that was a
bsent on red blood cells of their newborns were identified and a new c
ytological method, the Kleihauer-immunogold-silver-staining technique,
was applied on the blood of their neonates to detect and quantify mat
ernal red blood cells. Stringent precautions were taken to avoid conta
minations of neonatal blood samples by adult red blood cells. Results:
Maternal red blood cells were present in 3 newborns, a frequency of 4
% (95% CI: 1-11%), and the estimated volumes of hemorrhage were 0.8, 1
.5, and 101 mu l of maternal whole blood. No obstetric factor was clea
rly associated in this limited study with the occurrence of maternal-f
etal hemorrhage. Conclusions: Mother-to-fetus microtransfusion greater
than 1 mu l is infrequent at or near delivery, and it may be observed
after an uncomplicated pregnancy and vaginal delivery.