A baby begins life when a sperm from a man and an egg from a woman join together inside the woman’s body. Both the sperm and the egg are cells, tiny “building blocks” together containing all that is needed to create a new human life. Over a period of nine months, the cells divide again and again. The foetus (the term for a baby before it is born) grows and develops inside its mother’s womb (uterus). Eventually, the foetus is ready to be born. The period during which a foetus develops inside the womb is known as pregnancy.

Making a baby

Inside a woman’s body are two ovaries. These contain eggs—tiny round cells. Inside a man’s body are two testes. These contain sperm, hundreds of millions of tiny, tadpole-shaped cells. During sexual intercourse, the sperm swim into the woman’s body.

Inside the womb

The embryo moves to the woman’s womb. The womb is filled with warm liquid to keep the baby safe. Inside the womb, the cells carry on multiplying. After eight weeks, the embryo is about the size of a strawberry. It is now called a foetus. Food and oxygen are passed from the mother’s blood to the foetus through the umbilical cord. (This is cut when the baby is born, leaving a scar or “belly button”.)

A baby is born

It takes nine months before a baby is ready to be born. In the first few weeks, the heart, brain and spine form. By the 12th week, the foetus has nearly all its organs and its legs and arms have grown. After about 24 weeks, it is almost completely formed. It then steadily grows in size. When the baby is ready to be born, it usually turns round inside the womb so that its head is pointing downwards. Then, strong muscles in the womb push the baby along the birth canal and into the outside world.