What is progesterone? Progesterone is a hormone produced primarily in the female body. During pregnancy, progesterone secretion increases significantly. Progesterone maintains pregnancy by affecting the thickness and quality of the endometrium, protecting the embryo from the threat of miscarriage. Progesterone also helps reduce symptoms of nausea, vomiting, and fatigue during pregnancy. What is the progesterone value standard? The normal range of progesterone values during pregnancy depends on the stage of pregnancy. In early pregnancy, progesterone levels are approximately 10-44 nmol/L per liter. By late pregnancy, progesterone levels can reach 110-450 nmol/L per liter. If progesterone levels are lower than normal