Try as you might to remember to take your birth control and use a condom or sexual barrier — semen happens. Having potential progeny near your reproductive organs can be straight-up scary when you're just cuddling or dry humping and not expecting it, but can you really get pregnant through layers of clothes?
"Dry humping with jeans on, not so much, but let's say you have ejaculate or semen inside underwear in touch with vagina, there is a possibility, but it's not likely," says Draion Burch, DO, an Ob/Gyn.
Sure, a person's semen contains millions of "strong swimmers," but Dr. Burch says sperm is not strong enough to swim through clothes and into a person's vagina to impregnate them. The lifespan of sperm varies from person to person, but it generally can live for a few days inside a woman's reproductive tract, he says. As long as the sperm is alive, technically it can fertilize an egg, according to the Mayo Clinic, and it only takes one sperm out of the millions that are released in semen to do it. But a lot of sperm will die inside of a person's vagina on its trip to their eggs, even though technically that's a comfortable environment for sperm.
As for the towel some people use to wipe up semen after sex, that's pretty much the last place sperm wants to be, so it will die by the time the semen dries and definitely after a few hours. "Sperm has to be in the fluid in order to live, and without the fluid, sperm will die," Dr. Burch says. We know that semen is a mixture of sperm and a fluid released by the prostate gland, and once that fluid is dried, the sperm will also get dehydrated and die, Dr. Burch says.
Let's say you got naked, but didn't have penetrative penis-in-vagina sex, and your partner ejaculated near or around your vagina. Sperm could drip near your vulva (and, subsequently, your vagina) if you came into contact with semen, but even that would require some interesting physics to get you pregnant, so you are most likely fine.
It's also worth noting that if you do rely on the "pull-out method" to prevent pregnancy, it's not always foolproof, and 27 in 100 women who use the withdrawal method will get pregnant every year, according to Planned Parenthood. This statistic could be because of other reasons (like pre-cum and the birth control methods they were using), but having semen near or in your vagina definitely has to do with it. Dr. Burch also adds that if someone had semen on their hands, and then put their hands in their vagina, that could get someone pregnant, so it's important to keep your hands clean if semen is in the vicinity and you are pleasuring yourself or another woman with your hands.
Moral of the story? If you are a person who's not trying to get pregnant, be aware of the semen that's coming in contact with your body. It's a good idea to communicate with your partner about the types of birth control you plan to use, and be upfront with your gynecologist so they can give you the right information based on your lifestyle. The other reality here is that there are tons of factors that affect a person's ability to get pregnant in the first place, and it can be really hard for women to get pregnant, even when they're getting semen all up inside their vagina on purpose. So go ahead and cuddle and dry hump as hard as you'd like, but be careful.