Ovulation is the release of an egg from the ovaries. A woman is born with all her eggs. Once you start your periods, one egg (occasionally two) develops and is released during each menstrual cycle.
After ovulation, the egg lives for approximately 24 hours
Once the egg is released from the ovary it travels down the fallopian tube towards the womb. Fertilisation happens if sperm meets and fuses with the egg. Sperm can survive in the fallopian tubes for up to five days after sex.
If the egg is not fertilised, hormone levels fall, and the womb lining comes away and leaves the body as a period.
A woman cannot get pregnant if ovulation does not occur.