Progesterone’s Role in Pregnancy
Understanding a normal menstrual cycle
The menstrual cycle is the process by which, each month, a woman’s body prepares for a possible pregnancy. The average length of a menstrual cycle is 28 days, but not all women have a 28-day cycle. Normal cycles can range from 23 to 35 days and can vary from month to month.
The first day of a woman’s period marks the beginning of the menstrual cycle. During a woman’s period, the inner lining of the uterus, called the endometrium, is shed. Most periods last from 3 to 5 days.
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Once a woman’s period ends, the endometrium begins to thicken with the help of rising estrogen levels in the body. Around the 14th day of the menstrual cycle, the ovary releases a mature egg. This is called ovulation.
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During the 14 days following ovulation, 2 important events occur:
- The mature egg travels down the fallopian tubes to the uterus. (If an egg is fertilized by sperm, it generally occurs in the fallopian tubes)
- The ovaries begin to produce progesterone
Progesterone thickens and prepares the endometrium for implantation of a fertilized egg. If a fertilized egg implants into the uterus, the endometrium will remain thick to support the pregnancy. If the egg is not fertilized, progesterone and estrogen levels drop. This drop in hormone levels causes the endometrium to shed, prompting the start of a new menstrual cycle.
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%.