Fertility is neither a fixed value, nor set on a simple decline throughout your lifetime. Your fertility varies over the course of weeks according to where you are in your menstrual cycle. Today we’re looking at how you can boost your chances of getting pregnant by learning when you will be fertile.
The Fertile Window
The time in each cycle when you are fertile is called your fertile window, and it’s approximately six days long. Sperm can survive up to five days in the human body so your fertile windows starts around five days before you ovulate. The egg that is ovulated, meanwhile, is viable for a maximum of twenty-four hours so your fertile window only lasts a day after ovulation, for a total of six days.
If you’re trying within this six-day period, you have the best possible chance of success. If you’re slightly outside it, your chances are diminished, and your chances rapidly drop to zero as sperm simply cannot encounter the egg and fertilise it!
Finding the Fertile Window
A fertility calculator promises to tell you when you’re next going to be fertile. The most basic versions of these tools are the simplest to use but they provide the least accurate results. You simply give it some basic information about yourself – including the date of your last period and the length of your cycle, and it will make a best guess about when you will ovulate and therefore when you will be fertile (five days before that date).
Unfortunately this best guess isn’t personalised to you at all, and it’s simply not accurate enough if you’re trying to use this information to boost your chances of pregnancy (or to avoid pregnancy!).
You can get a more accurate answer if you’re willing to do tests that tell you what’s going on in your body specifically.
Ovulation predictor kits test the hormones in your urine, looking for the surge that causes ovulation. They’re similar to pregnancy tests, and are as widely available, making them a convenient option. It is possible to miss the LH surge if you take the test at the wrong time, or if you have an especially high or low level of Luteinising Hormone – either naturally or due to illness.
Basal body temperature tracking can be more useful, though it’s harder work for you. If you take your temperature every morning before you get up and your metabolism starts to heat your body, you can access this low level, your BBT. It responds to your body’s preparations for ovulation, which means it can show you when you’re ovulating. Apps that take their data directly from specialised sensors take a lot of the hard work out of your hands, leading to more accurate, helpful results.