A baby inside its mother’s wombA 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” 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.
When one sperm joins up with an egg it may fertilize it (1). The two cells, one from the woman and one from the man, combine to form a new cell (2). It is about the size of a full stop. As the fertilized egg grows, it divides into two (3). Then it divides again and again (4–6), until it becomes a small ball of cells, called an embryo.
If a newborn baby were to continue to grow at the same average rate as it did in the womb, it would reach a height of two kilometres (one and a quarter miles) by the time it was one year old.
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