What is the placenta?

The placenta is a temporary organ formed during pregnancy in mammals through the combination of the embryo's membranes and the mother's uterine lining. It serves as a medium for material exchange between the mother and the fetus. The placenta is typically disk-shaped, thick in the center and thinner at the edges, and has two distinct surfaces: the fetal side and the maternal side. The fetal surface is covered by the amnion, smooth and attached to the umbilical cord; the maternal surface is rough and uneven, closely adhering to the uterine wall. The size of the placenta correlates with the size of the fetus and the gestational age. At full term, the placenta has a diameter of approximately 16–20 cm, a thickness of about 1–3 cm, and weighs around 500 grams. Its primary functions include:

1. Nutrient supply: The placenta extracts oxygen and nutrients such as glucose, amino acids, and fatty acids from the maternal bloodstream and transfers them to the fetus to support its growth and development.

2. Waste removal: The placenta assists in removing metabolic waste products from the fetus, such as carbon dioxide and other metabolic byproducts, transferring them into the maternal circulation for elimination by the mother's body.

3. Immune protection and endocrine function: The placenta acts as a barrier, preventing most pathogens and harmful substances from entering the fetal circulation. At the same time, it synthesizes various hormones that maintain a stable pregnancy, support fetal development, and prepare for labor.

The placenta plays a crucial role during pregnancy and is expelled along with the fetus during childbirth. Its health directly affects fetal growth and development as well as pregnancy outcomes.