when does the placenta take over

The placenta typically takes over its key functions, such as hormone production and providing nutrients to the baby, around weeks 8 to 12 of pregnancy, with about 10 weeks being the average time for most women. Before this time, the corpus luteum (a temporary endocrine structure in the ovary) supports the pregnancy through hormone production, but by the end of the first trimester (around 12 weeks), the placenta fully takes over these roles. This transition includes the placenta producing hormones like progesterone and estrogen and directly supporting the baby’s nourishment by exchanging oxygen, nutrients, and waste products through the umbilical cord. The placenta also plays a role in reducing early pregnancy symptoms like morning sickness once it takes over hormone production. In summary, the placenta takes over around weeks 8 to 12, often considered fully functional by about week 10 to 12 of pregnancy.