What is progesterone? Before analyzing the symptoms and common causes of low progesterone, we need to first understand what progesterone is. Progesterone is a hormone that plays an important role in the female body. During pregnancy, progesterone can help maintain the lining of the uterus and reduce uterine contractions to avoid premature labor. At the same time, progesterone can also promote the development of breast tissue and breast milk secretion. Therefore, progesterone