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How Do You Know When You're Fertile?

Answering this question could make the difference between you getting pregnant and having to wait longer for that all-important positive result on the pregnancy test. While it’s well worth taking precautions when you’re not ready to start a family, when the time comes, you’ll discover that there are only a few days in each month (or, more accurately, menstrual cycle) when you are likely to get pregnant. If you know how to identify this time and predict it, you have an advantage when you’re trying to conceive.

The Fertile Window

Those days when you’re most likely to get pregnant are known as your fertile window, and they’re the five days before and day after you ovulate. It’s during these fertile days that sperm can survive long enough to reach the egg, within the 24 hours after it’s ovulated while it’s still viable and can be fertilised.

Outside this time, only particularly long-lived, fast moving sperm can reach the egg, and only a few days either side of the fertile window, conception is so unlikely as to be impossible.

Ovulation Tracking

It’s clear that your fertile window is ‘anchored’ by your ovulation date. To find out when you’re fertile, you need to discover when you’re going to ovulate and to do this with accuracy, you need technological help.

OPKs or ovulation predictor kits are hormone based tests that look for the Luteinising Hormone surge that causes ovulation in your urine. These tests are widely available and relatively simple to use – like pregnancy tests, you just immerse the test stick in your urine and wait for the results. Unfortunately, they are not always accurate so you might not get a positive result even when you are ovulating. Also, these tests can’t predict when you are going to ovulate, only confirm when you have ovulated.


OvuSense’s system gets you more accurate tracking, and a much stronger predictive value. Our sensor tracks your core temperature, and processes it with a clinically tested algorithm. The output – through the app that’s partnered with our sensor – can predict when you will ovulate in advance, giving you full access to the six or seven days of your fertile window.

Using a Calendar

If you know when you will ovulate – or have a very regular cycle, so you can rely on ovulating on the same day of your cycle each time – you can plot your fertile window on a calendar. Note the dates of your periods, and the date you ovulate (using either the results from OvuSense’s app or your knowledge of your cycle) and count back five days. This is the start of your fertile window. It ends one day after you ovulate. These six days are when you are at your most fertile and stand the best chance of getting pregnant!

To learn more about your cycle and hear from Ovusense customers visit ovusense