When does Placenta secretes progesterone to maintain the pregnancy?

The placenta starts secreting progesterone around the 7th week of pregnancy, after the corpus luteum's production of the hormone begins to decline. Progesterone is crucial for maintaining the uterine lining and supporting the pregnancy by preventing contractions and promoting an optimal environment for fetal development. As the pregnancy progresses, the placenta becomes the primary source of progesterone, which continues to be vital throughout the gestation period.