What is progesterone and what it does Progesterone is an important hormone that is critical to embryonic development during early pregnancy. It is mainly produced by the corpus luteum. A well-conditioned corpus luteum can produce enough progesterone to maintain pregnancy, provide sufficient nutrients, oxygen and prevent uterine contractions. Higher progesterone levels mean a better corpus luteum and a better chance of the embryo surviving and growing. Therefore, progesterone levels are crucial for fetal protection in early pregnancy. Standards and significance of progesterone levels in early pregnancy The normal range of progesterone levels in early pregnancy is 10~90ng/liter