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,
Studies of the Fetus in the Womb imbricato" ("Ask Biagino Crivelli's wife how the capon rears and hatches the eggs of hens when he is unplucked"). Da Vinci theorized that the umbilical cord was responsible for taking the fetus’ urine outside of the uterus. The studies were initially bequeathed to Francesco Melzi. In c. 1582–90 they were bought from his heirs by Pompeo Leoni and by 1630 they belonged to Thomas Howard, 2nd Earl of Arundel. Since 1690 the studies have been housed in the Royal Collection, United Kingdom. Studies of the Fetus in the Womb Studies of the Fetus in the Womb are two colored annotated