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How to Calculate Your Fertile Days

Finding out when you’re at your most fertile is key to making your conception plans. If you’re not able to target your fertile window, or fertile days, then you’re reducing your chances of getting pregnant quickly.

Today OvuSense is taking a look at how to calculate your fertile days, to give you some insight into the methods you need to be using, and confidence that you are doing so correctly.

What is the Fertile Window?

Your fertile window is not an arbitrary measure of fertility – it’s not simply when you happen to be most fertile. It’s a precise description of a biological window of opportunity. Sperm and eggs both have limited maximum lifespans: sperm can survive for around five days after ejaculation, while eggs have a maximum fertile life of only 24 hours after they’re ovulated.

The fertile window is when these two timespans overlap: when sperm can live long enough in the body to encounter that egg within it’s 24-hour life and fertilise it. Identifying it can give you a boost to your chances of getting pregnant.

The Best Way to Find Your Fertile Days

Some methods for finding your fertile days can be unreliable if you have an irregular menstrual cycle, or a hormone disturbance like Polycystic Ovary Syndrome. OvuSense relies on a method that gets results even in these cases: tracking your basal body temperature.

Your BBT is the low temperature your body falls to during a long period of rest. When you begin to get active, or even simply wake up, your metabolism speeds up and your body heats, swamping this low level. If you can access it, you can see patterns that reveal when you’re ovulating.

If you track your BBT across multiple weeks you’ll see it drops the day before you ovulate, then rises in the following three. Spotting this pattern can allow you to identify when you ovulate reliably and regularly.

Calculating Your Fertile Window

If you have a regular cycle, you can use your insight to calculate in advance when your fertile window will fall.

Mark the patterns from your BBT tracking on a calendar, along with the dates of the first day of your period across multiple months, you can see where in your cycle ovulation falls for you. Count from the first day of your period to the point where that drop occurs – if it’s a regular number of days across multiple cycles, then you can begin to mark it in advance, giving you the inside track on when you’re going to ovulate!

Find out more about core temperature technology and fertility here