When and Why do You Ovulate?

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[AD] Ovulation is one of the most important events for a woman’s health. It’s ovulation that is the reason for the menstrual cycle – the first half is your body preparing to ovulate, and the second half is the consequences: either fertilisation and pregnancy or ‘resetting’ ready for the following cycle.

It’s important to understand this process – if you’re trying to get pregnant, then it can help you interpret the results from your ovulation monitor or work out when you’re fertile with a calendar. If you’re not trying to get pregnant, then it’s helpful for you to understand these changes your body goes through each month.

The Menstrual Cycle

There’s no set date for ovulation – it all depends on your body. Some women have very regular cycles and can rely on ovulating not on the same date each month but the same number of days from the beginning of your cycle.

If you have a regular cycle, you can simply track ovulation using a calendar. You can note the first day of your period on the calendar, which is also the first day of your menstrual cycle. Counting forward from here, you can find when you’re going to ovulate. The first time you’ll need to use a confirmatory test like an OPK to make sure you know when you ovulate (approximately two weeks after your period starts).

What’s happening in that two weeks is known as your ‘follicular phase’. In this phase of your menstrual cycle, while your period is clearing away the previous cycle’s preparations for pregnancy in your ovaries more eggs are being prepared. Between five and seven follicles – small sacs filled with fluid – begin to develop towards being fully mature eggs.

One comes to dominate as the biggest and healthiest, and the others are reabsorbed by the body. It’s this egg that is ovulated and can be fertilised by sperm if they encounter it during its 24-hour lifespan.

Hormones

This process is caused and regulated by a number of different hormones. LH or Luteinising Hormone is one of the most important. It’s LH that cues the follicles to begin developing and, in a final surge, causes that egg to be released from the ovary into the fallopian tube.

You can use this to track when you ovulate. Ovulation Predictor Kits measure the LH levels in your urine. When they detect that characteristic surge of LH, they return a positive result and you know that you’ve ovulated!