In addition to these functions, the placenta has a very important hormonal role. This hormone is found in your bloodstream in measurable amounts within 10 days after fertilization. Pregnancy tests check HCG levels to determine if a woman is pregnant. The placenta also begins making the hormones estrogen and progesterone by the 7th or 8th week of pregnancy. At full term, a normal placenta is flat and has a cakelike, round or oval appearance.
Placentas vary widely in size and shape.
Sometimes it occurs without any obvious explanation. A small placenta may be found in normal pregnancies but may also be found with intrauterine-growth retardation. The part of the placenta that attaches to the wall of the uterus has a beefy or spongy appearance. The fetal side of the placenta, the side closest to the baby inside the amniotic sac, is smooth. It is covered with amniotic and chorionic membranes.