Whether you're trying to get pregnant or doing everything in your power to avoid it, knowing which days you're most fertile is some seriously valuable information. And it turns out that you can predict those ultra-fertile days by simply paying attention to a few clues from your body.
The first one is, obviously, your menstrual cycle. The first day of your cycle is the first day of your period. Then, somewhere around day 14 (or anywhere between day 11 and 21), you'll ovulate, meaning one of your ovaries will release an egg to be fertilised. It's during these days and the few directly before them that you're most fertile.
After this window, the American Pregnancy Association explains, an unfertilised egg will die within a day. Then, over the next few days, your progesterone levels will begin to decrease and your uterine lining will shed, starting the whole thing over again.
So, keeping track of the days of your cycle (possibly with the help of an app that spells it out for you) can clearly be immensely helpful if you're figuring out when you're ovulating. But because the days right before ovulation are going to be the most crucial, you will probably have to track your cycle for a month or two before being able to predict your fertile window.
To make your tracking even more accurate, you can pay attention to a few other clues. The first is your basal temperature, which can be measured orally or via your rectum. Your basal temperature rises right after you ovulate and stays high for a few days following that, Planned Parenthood explains. So, again, if you're trying to become pregnant, you'll want to have sex right before that happens — not after. That's why keeping tabs on your temp for a month or two will help you nail down the perfect timing.
And, if you're someone who generally has a fair amount of discharge, you can track that, too. Discharge is a product of both your vaginal and cervical mucus, and the cervix makes a bunch more during ovulation in the hopes that it will usher sperm into the uterus. This discharge tends to be stickier and more transparent (it's often said to resemble egg whites) than at other times of the month, so look out for that when you wipe or in your undies. The cervix itself also changes during your fertile days — it becomes softer and more open — and you can feel those changes happen by putting a (clean!) finger or two all the way inside your vagina.
However — major caveat alert – this is all obviously much easier if your cycles are around 28 days and on this side of regular. If they're not, it's worth checking in with your doctor for more guidance here. Plus, these markers only apply to people who are regularly ovulating. So if you're on hormonal birth control, for instance, your fertility isn't really changing throughout the month.
And, of course, it is still possible (though less likely) for you to become pregnant outside of your ovulation window. So if you're trying to avoid pregnancy, it's a good idea to use some form of birth control throughout your cycle. And, if you're actively trying to become pregnant, these are the days to go wild.