Also from reading the original paper in Science, we can see that perhaps the most important part of this process is that the baby's immune system learns to recognize the mothers as "self" so the baby's immune system doesn't attack the mother. There is also a similar, but less defined mechanism where the mothers immune system learns to recognize (or ignore) the baby, again so as not to attack it.
There is also a similar, but less defined mechanism where the mothers immune system learns to recognize (or ignore) the baby, again so as not to attack it.
Patrick