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How women become pregnant

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HealthWiki > A Book for Midwives > Chapter 3: A woman's body in pregnancy > How women become pregnant

About once a month, a woman's ovary releases a tiny egg. The egg moves down the tube and into the womb.
illustration of the below: a woman's reproductive parts, showing an egg in the tube.
The ovary releases a tiny egg into the tube.
Men make tiny cells called sperm inside of their testicles. When a man ejaculates (comes), a fluid called semen comes out of his penis. Millions of sperm cells come out in that fluid.
a man's reproductive parts.
The semen and sperm travel through this tube and out of the penis.
The sperm is made in the testicles.

If a man ejaculates inside a woman’s vagina during sexual intercourse, his sperm cells can travel through her vagina, through her womb, and into her tubes.

If the woman and man have sexual intercourse near the time of the month that the woman’s egg is moving down her tube, one of the man’s sperm cells may meet her egg. The egg may then plant itself in the lining of the womb. If this happens, the woman becomes pregnant.

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Every month that the woman does not become pregnant, the bloody lining of her womb comes out about 2 weeks after she releases the egg. We call this monthly bleeding, or menstruation.

How the baby grows

After a sperm and egg join inside a woman’s womb, they combine to become one group of cells that multiply and grow into a baby.

The mother’s blood contains oxygen from the air she breathes and nutrition from the food she eats. Her blood then passes air and food to the baby through the cord and placenta.

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When a woman is about
5 months pregnant, she
can feel the top of her
womb at her bellybutton.
MW Ch3 Page 30-2.png
When a woman is
9 months pregnant,
she can feel the top
of her womb just
below her ribs.

During the first 3 months of pregnancy, it is hard to see much happening from the outside. But inside the womb, the baby is forming organs, bones, and other body parts. During these early months, it is especially important that a pregnant woman avoid poisonous chemicals, unnecessary medicines, and alcohol, which can all harm the developing baby. As the baby grows, so does the womb. The mother can see her belly growing and can feel the womb by putting a hand on her belly.

a woman seen from the side, showing the baby upside down in the womb.
This is what you would see if you could look inside a pregnant woman´s womb.

Inside the womb, the baby floats in a bag of fluid called amniotic fluid (the bag of waters). The baby is connected to the placenta (afterbirth) by a cord, and the placenta is attached to the inside of the mother’s womb.

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When a person has difficulty having a child, he or she is infertile. For a couple that wants to have children, infertility can bring sadness, anger, or shame.

Often the woman is blamed when she does not become pregnant. Even if the couple gets medical help, many doctors will check only the woman for fertility problems. But often the man is the one who is infertile. Neither men nor women should be blamed for infertility. And both need support during this difficult time.

Infertility has many causes. Some cannot be prevented. But many causes of infertility are preventable.

a man who works with chemicals giving his clothes to a woman to wash.
Even washing clothes that have dangerous chemicals on them can harm fertility.
  • Sexually transmitted infections can leave scars inside a man’s or woman’s reproductive parts that prevent pregnancy.
  • Illnesses such as diabetes, tuberculosis, malaria, and mumps can cause infertility.
  • Dangerous chemicals from pesticides, cleaning products, or factories can get into the air, water, or food. These chemicals can make it difficult for a woman to get pregnant, or can harm the growing baby.
  • Smoking, chewing tobacco, drinking a lot of alcohol or using drugs can all harm fertility.

There are other causes of infertility that are not preventable. To learn more, look at a general health book like Where Women Have No Doctor.


When women grow older, they stop bleeding each month (menopause). They also stop producing eggs and lose the ability to become pregnant. This may happen suddenly, or slowly over 1 or 2 years. For most women, menopause happens when they are between 45 and 55 years old.

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During menopause, many women have some of these signs:

  • changes in monthly bleeding before it stops completely
  • suddenly feeling very hot and sweaty (hot flashes)
  • vagina becomes smaller and more dry
  • sudden changes in feelings

Many women are relieved when they do not have to worry about pregnancy anymore. As elders, women can share the wisdom of their years of life experience.

Men make sperm through most of their lives, even when they are very old.

This page was updated:11 Sep 2019