There’s a pretty basic fact about the female body that gets left out of most sex ed classes: most of the time, you have literally zero chance of getting pregnant, and the fertile period of your cycle is relatively short. The result is that lots of smart, capable adults who are otherwise fully equipped to navigate the world have no idea how the female reproductive system works.
Your Fertile Period is Short
The truth is, getting pregnant is not as easy as most people think. If you’re having sex once a week without any special effort to find the fertile period of your cycle, you only have about a 10 percent chance of conceiving per month.
Even under the most favorable conditions—two young, healthy people having frequent unprotected sex—there is still only about a 25 percent chance of getting pregnant in a given month. (This is mostly due to the Herculean effort required for sperm to successfully enter the egg. The sperm must be good quality, the cervical mucus must be optimal, and after the sperm fertilizes the egg, the embryo needs to be able to implant. It’s a complex piece of choreography where if one little thing goes wrong, the pregnancy doesn’t occur.)
You Can’t Lengthen Your Fertile Period, But You Can Do This…
The difference between a 10 percent and a 25 percent chance of conception is rather large. So how do you get as close as possible to 25 percent? By making sure you have sex during your fertile period.
Over 70 percent of pregnancies are conceived on the two days before ovulation, or on the day of ovulation itself. And since sperm can survive for up to five days in a woman’s body under favorable conditions (i.e. fertile cervical mucus), a woman is also considered fertile for two days before she enters her peak fertile period.
The fertile period closes conclusively very soon after ovulation. After the egg is released, it can survive for about 12 – 24 hours. If it doesn’t get fertilized by a live sperm during that time, the egg will die.
Don’t Make This Mistake
Many women, when they begin to track their fertile period, simply look at the dates of their period or use an app to estimate their ovulation day. If you have a super regular 28-day cycle, this may work fine for you.
But if your cycle is irregular, or if you’re still not pregnant after a few months of trying, think about this: only about 30 percent of women’s fertile periods fall entirely within the days of the menstrual cycle identified by clinical guidelines—that is, between cycle days 10 and 17. Some women reach their fertile days earlier, and others reach them much later. Even if your cycle is usually regular, using the calendar method or an app to predict your fertile period could be wildly inaccurate.
If you’re not getting pregnant as quickly as you thought you would, timing is the first thing you should consider. But for many women, it’s not enough to simply estimate your fertile window based on the dates of your period. Tracking your fertile period in a personalized way is the number one thing you can do to dramatically increase your chances of getting pregnant.