Conception occurs when as a result of sexual intercourse (or by an some medical procedure), a female egg is fertilised by a male sperm. Once a month, 14 days before the beginning of the next menstrual period, a microscopically small egg (ova) is released from one of a woman’s ovaries, and travels down a Fallopian tube towards the womb (uterus). During this journey, the egg may encounter sperm released by the woman’s male partner during intercourse.
If one sperm penetrates the egg, the egg is fertilised, in a process called conception, and if the fertilised egg successfully implants into the wall of the uterus, the woman becomes pregnant. Once an egg has been fertilised by one sperm, it immediately becomes impenetrable to other sperm, even though millions of sperm are deposited as a result of any single ejaculation.
If, perchance, two eggs are released and fertilised, there will be two babies or twins.