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Are you Fertile After Your Period?

Finding out when you are fertile is important when you’re trying to conceive, to give yourself an advantage. If you can consciously ensure your attempts to get pregnant are focused on the time when you have the greatest chance of success, then you have better odds of conceiving successfully and sooner.

Your period is a useful marker: while it doesn’t coincide with your peak fertility (or fertile window) it does send one very noticeable sign of when your cycle begins. As the rest of your menstrual cycle happens internally it can be difficult to place where you are within it, and when your fertile window will be.

To be able to calculate when you’re going to be fertile, and how long after your period that peak will be, you need to understand what’s happening in your menstrual cycle, the stages it moves through and how you can recognise them.

The Follicular Phase

In the follicular phase, your body is preparing eggs to be ovulated. Between five and twenty eggs are matured in small, fluid filled sacs called follicles. This begins at the start of your menstrual cycle, on the same day as your period starts.

The follicular phase normally lasts between 11 and 27 days, with the average being 26. If you have a very short follicular phase, coupled with a long period, you might be in your fertile window even as your period is happening, but it’s more usual for your fertile days to fall after your period has finished.


When the helathiest egg has grown to maturity, your endocrine system cues your ovaries to release it in a surge of LH – the Luteinising Hormone. That egg is released into the fallopian tubes, where it remains fertile for no more than 24 hours.

As sperm have a longer lifespan – they are themselves fertile for up to five days after ejaculation – you have a fertile window of around six days: five before ovulation and one following.

The Luteal Phase

After ovulation your body switches its focus: where previously your hormones were priming your ovaries to prepare that egg to be released, they are now directed at your uterus, to ensure it builds up a thick endometrial lining in which the egg can anchor if it is fertilised. It’ll begin to grow here, and become an embryo and then a foetus, as the lining itself develops into the placenta that nourishes it.

The luteal phase can last between 11 and 17 days, after which – if the egg wasn’t fertilised – you will experience your period as the whole cycle begins again.

Find out more about core temperature technology and fertility here