The female hormones estrogen and progesterone work together to prepare a woman's body to conceive a child each month. As an egg ripens in one of the ovaries, the lining of the uterus begins to proliferate under the influence of rising hormone levels, according to Dr. Lauralee Sherwood in her book, "Human Anatomy." Once an egg is ovulated, if fertilized, it will implant in the uterine lining. Progesterone from the corpus luteum, a part of the ovary, then maintains the uterine lining until the placenta forms.
High progesterone levels don't preclude normal reproductive function, but they can exacerbate some of the side effects of the menstrual cycle. Many women experience headaches, moodiness, breast tenderness and fatigue as they approach their period. It is during this time that progesterone levels are highest. Women who have particularly high progesterone levels tend to have more severe pre-menstrual symptoms than those with naturally lower levels, Sherwood says. For most women, progesterone-related side effects diminish as hormone levels drop later in the cycle.
Non-pregnant women who are not on birth control pills or hormone supplementation naturally experience their highest progesterone levels approximately one week after ovulation, with levels falling and side effects diminishing in the subsequent week. For women who are pregnant, however, progesterone levels increase dramatically in the early weeks of pregnancy, leading to many of the classic first trimester symptoms, according to Heidi Murkoff and Sharon Mazel in their book, "What To Expect When You're Expecting." Exceedingly sore breasts, frequent headaches, moodiness and nausea are all commonly associated with early pregnancy. While these symptoms of high progesterone are similar to the symptoms experienced by non-pregnant women during their natural high-progesterone phase of the menstrual cycle, they're exacerbated by the extremely high levels of the hormone associated with pregnancy.
Some women require progesterone supplements. Birth control pills may contain progesterone analogues, menopausal women occasionally use progesterone to alleviate uncomfortable symptoms and prevent disease, and pregnant women who have low progesterone may be prescribed progesterone supplements to prevent miscarriage. Drugs.com notes that the side effects of high progesterone associated with supplementation are similar to those of high progesterone that's produced naturally by the body. In particular, supplement-related side effects may be even more exacerbated than those related to normal hormone production, because progesterone levels may become quite high. Women frequently note vomiting, dizziness and cramping in addition to the typical symptoms of progesterone associated with menstruation or pregnancy.
For women experiencing effects of high progesterone due to a normal menstrual cycle, there's little that can be done to alleviate discomfort aside from waiting for the high progesterone phase to pass, which it will in approximately a week. Pregnant women, or those on hormone supplementation, though, are subject to high progesterone for long periods of time. Murkoff and Mazel note that almost everyone begins to adjust to high progesterone after a few months, meaning that symptoms gradually subside with time.