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Home > A-Z Health Topics > Pregnancy > Before you get pregnant: Information for all women > The menstrual cycle

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The menstrual cycle

Diagram of the female reproductive system. The blood and tissues lining the uterus (womb) are breaking down and sheding from the body. Day 1 starts with the first day of your period. This occurs after hormone levels drop at the end of the previous cycle, signaling blood and tissues lining the uterus (womb) to break down and shed from the body. Bleeding lasts about 5 days.
Diagram of the female reproductive system. Fluid filled pockets have formed on the ovary. Usually by Day 7, bleeding has stopped. Leading up to this time, hormones cause fluid-filled pockets called follicles to develop on the ovaries. Each follicle contains an egg.
Diagram of the female reproductive system. A follicle has developed and reached maturity. The lining of the uterus has started to thicken. Between Day 7 and 14, one follicle will continue to develop and reach maturity. The lining of the uterus starts to thicken, waiting for a fertilized egg to implant there. The lining is rich in blood and nutrients.
Diagram of the female reproductive system. The follicle has burst and released an egg from the ovary. Around Day 14 (in a 28-day cycle), hormones cause the mature follicle to burst and release an egg from the ovary, a process called ovulation.
Diagram of the female reproductive system. The egg travels down the fallopian tube. Sperm have entered the fallopian tube and are approaching the egg. Over the next few days, the egg travels down the fallopian tube towards the uterus. If a sperm unites with the egg here, the fertilized egg will continue down the fallopian tube and attach to the lining of the uterus.
Diagram of the female reproductive system. If the egg is not fertilized, hormone levels will drop around Day 25. This signals the next menstrual cycle to begin. The egg will break apart and be shed with the next period.

Content last updated September 27, 2010.

Resources last updated September 27, 2010.

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womenshealth.gov
A federal government website managed by the Office on Women's Health in the Office of the Assistant Secretary for Health at the U.S. Department of Health and Human Services.
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