If a woman's on top, is there a chance of pregnancy if a little sperm went in?

If sperm⁠ (sperm: Reproductive cells of people with penises which can fertilize an ovum and create pregnancy.) went into a vagina⁠ (vagina: The internal passage leading from the opening of the vulva to the cervix of the uterus.) and the person with the vagina is not on any form of birth control⁠ (birth control: Any number of methods people use to intentionally prevent unwanted pregnancy, including the condom, the cervical barrier, the implant, the patch, the pill, the rhythm method, the ring, the shot, the IUD, spermicide and withdrawal.) , then YES, they could get pregnant.

Even if they’re on top⁠ (top: In sexuality, this is someone who wants to take the/a lead during sex with a partner or partners, or to consensually take the role of being in charge of sexual actions.) , and some semen⁠ (semen: Fluid which comes from the urethra of the penis during ejaculation, and which usually contains sperm.) trickles out⁠ (out: Short for ‘out of the closet’. When someone’s LGBTQ+ identity is known to other people.) , chances are just enough sperm cells could make their way up into their reproductive tract to result in a pregnancy⁠ (pregnancy: The state of carrying a developing embryo or fetus within the uterus. Medically, someone is considered to be pregnant when an egg has been fertilized by sperm, cells divide, and the fertilized egg is implanted within the lining of the uterus.) . Bear in mind, the body of someone with a uterus⁠ (uterus: An internal, muscular reproductive organ in the pelvis. During pregnancy, this is where a fetus will develop. The lining of a person’s uterus is also the thing that sheds every menstrual cycle in what we call a period.) is built to get pregnant. At the right times of their cycle, there are various physiological mechanisms to facilitate sperm travel up to an egg (as well as mechanisms to bring the egg to the sperm). Nature – whether you want it to or not – wants to cause pregnancy.

If you are going to engage in “dry sex⁠ (dry sex: A kind of sex where people have clothes on, but are pressing their genitals together. This can also be called frottage, grinding or dry humping.) ,” you should still wear a condom⁠ (condom: A thin sheath or tube of latex or another material, worn over the penis during sex to prevent or reduce the risk of pregnancy and/or sexually transmitted infections.) to prevent unwanted pregnancy and infections. And if it has been less than 120 hours since the sexual⁠ (sexual: About or relating in some way to sex or sexuality.) encounter in question, the person who can get pregnant can take emergency contraception⁠ (emergency contraception: A method of contraception used to prevent pregnancy after sex or rape has already occurred, rather than used before or during, like most types of contraception. Includes emergency contraception pills and IUDs.) to prevent pregnancy. Otherwise you would have to wait and see if they get pregnant.

For future reference, please read:

• What’s the Risk? Easy Pregnancy Risk Assessments
• Safe, Sound & Sexy: A Safer Sex How-To
• Hey, Boyfriend! Male Reproductive Choices
• Emergency Contraception
• 10 Common Myths, Misunderstandings and Big Ol’ Lies About Emergency Contraception