Birth stage three, which begins after the birth of the baby, further contractions expel the placenta, amniotic sac, and the remaining portion of the umbilical cord usually within a few minutes. Enormous changes take place in the newborn's circulation to enable breathing in air. In the uterus, the unborn baby is dependent on circulation of blood through the placenta for sustenance including gaseous exchange and the unborn baby's blood bypasses the lungs by flowing through the foramen ovale, which is a hole in the septum dividing the right atrium and left atrium. After birth the umbilical cord is clamped and cut,
Umbilical cord prolapse to congenital anomalies or prematurity, however. It is considered an emergency. The first sign of umbilical cord prolapse is usually a sudden decrease in fetal heart rate that is severe and does not immediately resolve. On a fetal heart tracing, this would usually look like moderate to severe variable decelerations. Occasionally, the cord can be seen or felt on vaginal examination, particularly with overt cord prolapse. Risk factors that are associated with umbilical cord prolapse tend to make it difficult for the fetus from appropriately engaging and filling the maternal pelvis or are related to abnormalities of the umbilical cord.