A quick note since this has come up a few times....

In theory, the blood in the "placental curcuit" belongs to  the baby - the
moms blood in the uterine vessels interfaces with the baby's blood through
diffusion, etc - but not by direct mixing.

However, in practice some maternal fetal transfusion can occur.  The test
to evaluate this is the KB [Kleihauer-Betke stain] test which looks for
maternal cells in the newborn's circulation.

The scenario where this is most common is with precipitous delivery,
placental abruption, placenta previa, tetanic labor or manual removal of
the placenta.  It can also occur during version [turning the baby inside
the mom - done from the outside]


Gail
Gail Hertz, MD, IBCLC
Pediatric Resident
author of the little green breastfeeding book - disclaimer: owner of Pocket
Publications