The hormonal changes in the female body cause a single egg to be released from the ovaries every month. This egg journeys through the fallopian tubes into the uterus – the lining of the womb thickens at the same time as this, in order to prepare for the possibility of the egg becoming fertilised and developing into a baby. If this doesn’t occur, the lining of the womb is passed out of the body in the form of a period – most women have a monthly cycle once every 28 days, but the length of this and the time of the cycle can vary between women. Anywhere between 24 and 35 days is normal and common among women. Having unprotected sex during the phase of the egg being released can result in the sperm fertilising the egg whilst it’s in the fallopian tube – as this, now fertilised, egg journeys through the tube, it eventually becomes embedded in the lining of the womb, where it will start to develop.
In the time frame of 12 to 24 hours after the egg has been released from the ovaries, the egg can be fertilised. The sperm can survive in the fallopian tubes for up to a week, so even if the egg hasn’t been released yet, it is still possible to get pregnant. During the conception period, a single sperm penetrates the female’s egg – this sperm carries the genes of the father, and once it has entered the egg, no other sperm can penetrate. This fertilised egg is known as a zygote – until eight weeks after the conception, which it then develops into an embryo, and then a foetus after this time. A missed period is often a sign of pregnancy, so a urine test can often determine if you’re pregnant.