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How the Female Reproductive System Really Works


Updated June 27, 2014

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Long Before Menstruation Begins
Baby girl with pink towel

When a baby girl is born, she has two million eggs in her ovaries.

Photo: tec_estromberg / flickr

The female reproductive system is highly complex, and for everything to work just right, several hormones, glands, and organs must do their jobs in the right order, at the right times. Once you understand how the reproductive system works, it's easier to understand how things can go wrong. It's quite a miracle that things go right at all, given how complicated the entire system is!

Also, being familiar with how the reproductive system works can help you understand why certain fertility treatments are done at specific times.

Familiarity with the reproductive system may even help you understand how to get pregnant faster, by helping you time sex for ovulation.

Long Before Menstruation Begins

We often think of the reproductive system as something that works in monthly cycles, just like our menstrual cycle. While this is mostly true, it's much more complicated than that.

The egg you may ovulate this month has been getting ready inside a follicle for the past 290 days, almost 9 months. In fact, that egg has been around as an immature egg since you were just a fetus inside your mother's uterus.

When you were just a wee one, at about 12 weeks gestation, your ovaries contained 6 to 7 million immature eggs –- the most you would ever have in your life. By the time you were born, there were only 2 million immature eggs left, and by the time you had your first menstrual cycle, your ovaries held just 500,000.

What happens to all those millions of potential eggs? Where do they go?

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  4. Ovulation, Sex for Pregnancy, and Reproduction Basics
  5. Female Reproductive System: Long Before Menstruation

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