How Ovulation works

Short Answer: Ovulation is the process in which a mature egg is released from an ovary.

It is a common misconception that a woman can get pregnant at any time of the month. In fact there is only a short ‘window’ in the menstrual cycle during which you are fertile. So, when is this fertile period? And why are you only fertile for such a short time? To answer these questions, we should first understand ovulation.


Ovulation is a process that occurs once every cycle (there are rare exceptions to this). It will happen around 14 days before the start of your next period, roughly half way through your cycle. The process involves one of the ovaries releasing an egg. Whilst contained in the ovaries, eggs develop in tiny sacs called follicles. At the start of each menstrual cycle a few follicles will be selected as candidates for this cycle’s ovulation. Eventually all but one will die off, with the remaining one becoming the dominant follicle.


Around this time there will be some changes in hormone levels inside a woman’s body. Oestrogen will increase, causing the lining of the uterus to thicken in preparation for a potential pregnancy. It also helps to create an environment less hostile towards sperm to improve chances of fertilisation. Then comes the surge in luteinising hormone (LH). LH is what causes the dominant follicle to release it’s mature egg from the ovary. Once released, the egg will travel down the Fallopian tube where it awaits fertilisation.


The egg can only survive for around 24 hours in the Fallopian tubes. If it is not fertilised it will die and be absorbed into the lining of the uterus. It will then leave the body during menstruation. So, if you are attempting to get pregnant, the egg must meet a sperm within 24 hours of ovulation. Sperm can actually survive for 3-5 days, meaning the few days before ovulation and the day of ovulation itself make up the ‘fertile window’. These are the days on which to have sex if you are looking to get pregnant.


All of this means that knowing when you are ovulating can be very helpful. If you want to know when you are ovulating then look out for the following signs:

  • Change in cervical fluid – You may notice larger amounts of cervical fluid. The fluid is also often wetter, more slippery and clearer than usual.
  • Change in body temperature – Often there will be a slight increase in body temperature around the time of ovulation. You may find you can detect this with a thermometer.
  • Change in cervical position – The cervix will often be raised during ovulation.

It’s also possible to use ovulation test kits, which are available at most chemists or pharmacists. Alternatively you could use our ovulation calculator to pinpoint your fertile days.