When does babys blood mix with the moms during birth?

During birth, the baby's blood can mix with the mother's blood primarily during the placental separation phase, when the placenta detaches from the uterine wall. This typically occurs after the baby is delivered but before the placenta is expelled. While the circulatory systems are separate during pregnancy, small amounts of fetal blood can enter the maternal bloodstream, particularly during labor and delivery. This mixing can also happen if there are any tears or breaks in the placenta or umbilical cord.