placental circulation

They described the human embryo from the first division of the ovum until placental circulation takes over.

After 14 weeks the lymphatic system is likely to have developed sufficiently to drain away any excess fluid, and changes to the placental circulation will result in a drop in peripheral resistance.

The immediate haemodynamic effect of interrupting blood flow to the low resistance placental circulation while the umbilical arteries are pulsating is an abrupt rise in systemic arterial pressure with possible deleterious effects.

Another cause factor is determined to be monochorionic twin pregnancies, involving the death of one twin in the second trimester, which in turn causes vascular exchange to the living twin through placental circulation through twin-to-twin transfusion, causing hydranencephaly in the surviving fetus.

The umbilical and placental circulation system differs from the regular circulation in that veins, not arteries, carry the oxygenated blood to the fetus, and arteries, not veins, carry away the oxygen-depleted blood, with the waste products, back to rejoin the mother's blood supply.