Final answer:
Placenta previa is a condition where the placenta blocks the cervical opening, leading to delivery complications and potential antepartum hemorrhage. The baby might need to be delivered via cesarean section, and if the placenta is retained, medical intervention is required.
Step-by-step explanation:
When the placenta blocks the os of the uterus, a condition known as placenta previa occurs. This condition can cause complications during delivery as the baby's exit path through the cervix is obstructed. Placenta previa can lead to antepartum hemorrhage and may require a cesarean section to safely deliver the baby. After the baby is born, the umbilical cord is cut, and the baby begins to breathe independently as carbon dioxide builds up in the blood, triggering the respiratory response. The placenta should then be delivered during the final stage of labor. If it does not, the condition is considered a retained placenta, and intervention by a healthcare professional might be necessary.