It Sticks Around Longer Than You Think
Sperm typically stays in your body for 48 hours after s*x, however, “it can hang around for as long as five days to a week,” depending on how “friendly” your cervical mucus is, says Fisch. Interestingly, cervical mucus protects sperm and helps it stay longer in the body around ovulation, when you’re most fertile.

Your Guy’s Health Affects His Sperm
“Sperm may be healthier for men under 40,” says Wambach. “And they’ll definitely be healthier in men who avoid things like smoking, a high-fat diet, and environmental toxins.” So if you’re considering starting or expanding your family, keep that in mind.

Temperature CAN Lower His Sperm Count
Apparently, his semen fluctuates with the seasons. “Sperm count tends to be lowest in summer months and highest in winter months,” says Fisch, because exposure to heat lessens sperm count. Overheating can include anything as seemingly innocuous as your man having a hot Macbook on his lap or as obvious as the two of you relaxing in a hot tub. “In a Jacuzzi 104 degrees and higher, sperm count can decrease dramatically,” warns Fisch. In fact, this decrease can last for months after extreme overexposure to high temps. “I tell my patients, if you’re trying to have kids, don’t go into hot tubs.” Of course, don’t assume you’re totally safe from getting pregnant after you take a dip, either. “It’s not birth control,” he laughs.

Male and Female Sperm are Created Equal
Sperm either have the X or Y chromosome, but their chances of making it don’t differ, says Fisch. The idea that one type is more resilient or swims faster than the other is just a myth.

It’s Super Rare to Be Allergic to Sperm
We’ve all heard that women can be allergic to sperm, causing inflammation or redness, but both Fisch and Wambach say that it’s very, very rare to be allergic. “I’d look to other factors, like a vaginal infection, first,” says Fisch. There has also been one study on a sexually transmitted allergy to Brazil nuts (where a woman had an allergic reaction to her partner’s sperm after he ate the nuts). But again, cases like this are extremely rare. In the unusual case you are diagnosed as allergic, wearing a condom can prevent irritation.