How long do placentas function?

Placentas function throughout the entire duration of pregnancy, which typically lasts around 40 weeks or approximately 9 months in humans. Their main role is to facilitate the exchange of oxygen, nutrients, and waste products between the maternal and fetal circulatory systems. However, the placenta doesn't start forming until after the embryo implants into the uterine wall, which occurs about a week after fertilization.

During pregnancy, the placenta grows and develops alongside the fetus, ensuring a constant supply of essential substances and removal of waste products. The placenta also produces various hormones that are crucial for maintaining the pregnancy, such as progesterone, estrogen, and human chorionic gonadotropin (hCG).

Once the baby is born, the placenta is no longer needed and is expelled from the uterus during the third stage of labor, also known as the placental stage. This process is typically accompanied by mild uterine contractions and may involve the release of additional fluids and tissues. The placenta is often examined by healthcare professionals to evaluate its condition and ensure that it has been completely expelled.