Fertility Facts: 5 Things You Should Have Learned in Sex Ed—But Didn’t
If you’re like most women, you spent your young adult years trying not to get pregnant. And quite possibly, you had no idea how your menstrual cycle actually related to fertility. Maybe you feared that if you even thought of the word penis, you’d get pregnant. But then later in life, when you actually wanted to have a baby, you realized it wasn’t quite that easy. And all of a sudden: understanding your cycle and how it relates to fertility became very important.
Here, we’ll review 5 fertility facts every woman needs to know—whether she is trying to conceive or not.
1. You’re only fertile 6 days per month
The truth is: you can only conceive six days per cycle. Only six! That means you’re fertile for about 20 percent of each month. So, if you’re trying to conceive, 80 percent of the time is waiting until you can try again. This is why tracking your cycle can be extremely valuable, as it will shed light on when you ovulate.
Knowing when you ovulate is important because it will tell you your personal 6 fertile days—it’s not the same for everyone—so you can have sex with your partner on those days. This is the key to getting pregnant: having sex on your fertile days. Your fertile days are the five days before ovulation, and the day of ovulation itself. (For more information, check out our post on the best time to get pregnant.)
2. You can conceive after age 35
You might have heard of a myth out there called the “fertility cliff.” The idea (based on a study that happened in the 1600s, yes, you read that right!) is that after age 35 your fertility falls precipitously. But the fertility cliff is false. While your fertility does decline with age—it happens gradually over time. The reason is that at birth, women have a finite number of eggs (or oocytes) in their ovaries. And with age, both the quantity and quality of those eggs declines gradually.
A study of women from a more recent century (the 1990s) found that for women between 27–29 years old, the probability of conception was about 80 percent within a year of trying to conceive, and for women between 35–39 years old, the probability was about 77 percent. Only a 3% drop in fertility odds!
Our friends at Healthline put together this infographic below, which shows how your fertility changes as you age. The takeaway? Age does play a role in your fertility, but there is not a sharp cliff at the age of 35.
(For more information, check out our post on your chances of getting pregnant in your 20s, 30s and 40s.)
3. Your cycle is variable
Remember your 6 fertile days? Well, they can be tricky to find: Your body doesn’t follow a Swiss train schedule. A study from 2006 followed 141 healthy, regularly cycling women for up to a year so that researchers could better understand the average menstrual cycle. According to the classic calendar method, the menstrual cycle lasts 28 days, and ovulation occurs perfectly in the middle on cycle day 14. This would mean that the two phases of your cycle (follicular phase and luteal phase) are each 14 days long.
But, that’s not what the researchers found. They found that on average, the follicular phase was about 16.5 days, putting the average day of ovulation on CD 16, two days later than classically predicted. They also found that while the average cycle length was 28 days, about 43 percent of the women had at least seven days of variability from cycle to cycle.
The takeaway? Your cycle is variable and your fertile days (those 6 days each month that you can conceive) don’t follow a schedule. Again, this points out how cycle tracking can help you pinpoint your fertile window.
4. You are more fertile on some days than others
Back to those 6 fertile days—you are more likely to get pregnant on some of those days than on others. In fact, according to research, here are your most fertile days, ranked in order:
- Sex on one, two, or three days before ovulation = 20–30% chance of getting pregnant
- Sex four days before ovulation = 10–12% chance of getting pregnant
- Sex five or six days before ovulation = 0–5% chance of getting pregnant
(For more detail on this, read our post on your personalized fertility calendar.)
5. Sexual positions don’t affect your chances of conception
One question that couples often wonder about when trying to conceive is whether or not certain positions during or after sex can increase the likelihood of getting pregnant. Should you stay on your back? Should you raise your legs in the air, so gravity makes the sperm travel better?
Should you dangle from the ceiling like a bat for the absolute most gravity-related assistance? The answer is no. Pretty much as long as he ejaculates during sex, and sperm goes into the vagina, positions during or after sex don’t affect odds of conceiving.
But what can help? Figuring out how often you should have sex to get pregnant. (The short answer? Every other day—or every day if you’d like!—during your fertile window.) Again, it all comes back to the fertile window and those 6 days that you can conceive each cycle.