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Progesterone’s Role in Pregnancy
The hormone progesterone is often called “the pregnancy hormone” because it plays 2 important roles in pregnancy:
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Progesterone thickens the endometrium
Throughout an average 28-day menstrual cycle, the thickness of the endometrium varies. (The menstrual cycle begins on the first day of a woman’s period. For more information on a normal menstrual cycle, click here.)
During the first 14 days of the menstrual cycle, the endometrium is relatively thin and begins to thicken before ovulation. After ovulation, the endometrium continues to thicken. If no pregnancy occurs in this cycle, the endometrium will shed during a woman’s period and become thinner. If pregnancy occurs, the endometrium will remain thick to support the pregnancy.
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The difference in the thickness of the endometrium varies depending upon the amount of progesterone in the body. The endometrium is thinnest during the first half of the menstrual cycle, when progesterone levels are low. The endometrium becomes thickest after ovulation when progesterone levels rise.
The increasing levels of progesterone after ovulation are important to prepare the uterus for implantation of a fertilized egg.
Progesterone supports pregnancy
After a fertilized egg implants in the endometrium, the ovaries continue to produce progesterone to provide a nourishing environment for the growing embryo.
During a normal pregnancy, around 8 weeks after implantation, the placenta takes over the production of progesterone from the ovaries. The placenta produces a significant level of progesterone to maintain a healthy pregnancy.
Important Safety Information
The most common side effects of CRINONE (progesterone gel) 8% include breast enlargement, constipation, drowsiness, nausea, headache, and pain in the pubic area. You should not use CRINONE 8% if you have any disorders involving blockage of your blood vessels, or a history of these disorders, miscarriages, vaginal bleeding that hasn’t been diagnosed, liver problems or disease, or known or possible cancer of the breast or genital organs. You should discontinue use of CRINONE 8% if any symptoms occur that signal a blockage of your blood vessels. There is no adequate evidence that CRINONE 8% will work in preventing miscarriage. Your doctor should examine your breasts and pelvic organs, as well as perform a Pap smear prior to prescribing CRINONE 8%. If you have vaginal bleeding during treatment with CRINONE 8%, your doctor should look for the cause. If you have conditions that cause fluid retention, a history or depression, or diabetes, your doctor should provide special attention to your care while you are using CRINONE 8%.