This occurs when a mother with and
Rh- blood factor has a
Rh+ baby. When trans-
placental leakage occurs, 3-4 days before labor, the mother's
Rh- blood is exposed to her baby's
Rh+ blood. The mother creates
antibodies against her baby, which
subsequently flows back into the baby's bloodstream, causing
agglutination (blood clumping). The effect is that the baby comes out of the mother and a blood
tranfusion must be performed within 5-8 minutes of birth in order for the baby to survive.
This can only occur on the mother's second Rh+ baby. If this
phenomenon occurs to the first baby, a
sensitizing dose takes place. This will cause the mother to build up
antibodies againt the
Rh+ positive baby's, but the
titer (ratio of white blood cells to red blood cells) will not be high enough to severly damage the baby. However, the second time, an
eliciting dose occurs, and the mother is able to build up
antibodies far more rapidly against her baby's
invasive blood.