How pregnancy happens.
Each month a girl or a woman produces an ovum (egg) from one of her ovaries. This egg is released into the fallopian tubes, where it travels down to the uterus (womb). If the egg is not fertilised by a man’s sperm it will come out of the uterus, through the vagina, together with the blood rich lining of the womb, in the form of a monthly period.
If a man and woman have sex then there is a chance that the egg may become fertilised. This normally happens in the fallopian tubes, the fertilised egg then travels down into the womb, where it becomes attached to the lining of the uterus and begins to grow.
Sperm are produced in the testicles. They travel up the vas deferens (tubes) and mix with the semen that is produced in the seminal vesicle. When a man ejaculates during sexual intercourse, this mixture of sperm and semen come out of the end of the penis and are released into the vagina. The sperm can then swim until they meet the egg inside the woman’s body.
Millions of sperm are released, but it only takes one sperm to fertilise an ovum.