Women have a ton of misconceptions about their fertility, according to a recent study in the journal Fertility & Sterility, Fox News reports. 

Check out some of the most common myths the study uncovered, and get the facts behind each one.

Myth #1: Your Weird Period Won’t Affect Your Chances of Getting Pregnant

If your time of the month is wildly unpredictable, it can definitely impact how long it takes you to get pregnant. If you have only a few periods a year, you’re automatically reducing your probability of conceiving, says study author Lubna Pal, associate professor of obstetrics, gynecology, and reproductive sciences at Yale School of Medicine. And if your cycle varies in duration from month to month, it’ll be harder to pinpoint exactly when you’re ovulating.

Myth #2: Having Sex More Than Once a Day Will Up Your Odds of Getting Pregnant

“Unlike a woman, who releases one egg each cycle, in an ejaculate there are millions of sperm, and only one sperm is needed to do the job,” says Pal. 

Myth #3: That STD You Had in Your 20s Probably Didn’t Affect Your Fertility

More than one-quarter of women don’t know the impact that STDs can have on fertility. Unfortunately, many STDs like chlamydia, gonorrhea, and pelvic inflammatory disease can result in damage to your fallopian tubes, says Pal. And when your tubes are blocked, the chances of sperm and egg meeting are decreased. Even if they do meet, your odds of having an ectopic pregnancy increase with tubal damage.

That’s why it’s crucial to diagnose and treat STDs as soon as possible, says Pal. And if you’ve had a history of STDs, consult your physician as soon as you’re ready to get pregnant in order to identify any damage and improve your odds of conceiving.

Myth #4: Getting Older Doesn’t Have a Huge Impact on Fertility—Tons of Women Have Babies in Their 40s!

Shockingly, one-fifth of women are unaware of the effects of aging on fertility. While it certainly seems like many women are getting pregnant later in life, that doesn’t mean it’s easy to get pregnant past your mid-30s. In general, it’s around age 36-37 when you see a change in your ability to conceive, says Pal. “It takes longer to get pregnant, you’re more likely to miscarry, and more likely to have a child with genetic abnormalities such as Down syndrome.”

Myth #5: Certain Sex Positions Increase Your Chance of Getting Pregnant

No, gravity doesn’t play a role in getting you pregnant, though more than one-third of women think specific positions could work better than others.