When you reach the time in your life when you start to think about starting a family of your own, you’ll start to hear the word fertility a lot. Not just from the doctors and specialists you’re consulting about your preparations for pregnancy, but in your own research, in the marketing and advertising for ‘fertility supplements’ and devices like a ‘fertility sensor’, which purports to help you get pregnant.

If you’re going to make your own informed decisions about all of these products and issues, you need to understand what people mean when they use the word fertility: we have an instinctive understanding of what it means, neither that, nor the standard dictionary definition always match the specialist circumstances in which it’s being used.

When Your Doctor Talks About Fertility

‘Fertility’ in the medical sense means ‘the ability to get pregnant and bear children’, and when you’re talking with your doctor about your fertility, they’re often expressing the concept of ‘your chances of getting pregnant over a given period’.

The same follows for infertility: this is a diminished or absent ability to bear children, and it’s often diagnosed as an observation: couples who have been unable to conceive despite trying regularly through unprotected sex over a three year period have only a 25% chance of conceiving in subsequent. In some cases, a cause may be discovered, but in over a quarter, it’s never clear why pregnancy is difficult or impossible.

‘Fertility Monitors’

Companies that make fertility monitors are using the word differently to doctors. These devices, apps and tests aren’t telling you about your fertility in any absolute sense: they don’t tell you how easy or difficult it is for you to get pregnant compared with a universal standard, or diagnose why you might not be getting pregnant.

Commercial fertility monitors are useful because they tell you when you are fertile, or more specifically when you ovulate. You can only get pregnant when can sperm encounter and fertilise an egg, no more than twenty-four hours after it’s ovulated. ‘Fertility monitors’ read your hormones, period frequency, temperature, or best of all a combination of these three and more factors to predict when you’re going to ovulate or confirm when you are ovulating.

The most helpful of these devices give you a prediction well in advance of your ovulation date: this means you can plan in advance and take full advantage of your fertile window: the five days before ovulation when sperm can survive long enough to meet the egg when its ovulated, and the day after, while the egg is still viable.

Accurate predictions like this can boost your fertility in the medical sense by giving you an improved chance of getting pregnant.