According to the NYU Medical Center, the chances of getting pregnant from a given sexual encounter are completely independent of whether the woman has had sex before or not. Regardless of how often a woman has had sex, should sperm and egg meet, fertilize and attach to the uterine lining, a pregnancy can occur.
Upon the male's ejaculation into the vagina, the sperm cells begin traveling up the birth canal, through the cervix, and into the fallopian tubes where the oocyte (egg) is waiting, as described by New York University Medical Center. Although many sperm find their way to the egg, only one sperm makes it into the egg and successfully combines DNA with it. Then, the fertilized egg travels back up the Fallopian tube and attaches to the portion of the uterus that later becomes the placenta. Then, pregnancy continues as normal.
The process of getting pregnant works the same for every woman's reproductive system, NYU Medical Center says. It is possible, in fact, for a woman to get pregnant the first time she has sex. Contraceptive methods such as the morning-after pill, spermicidal lubricant and condoms greatly decrease the chances of pregnancy by preventing sperm and egg from making contact. However, no method is entirely foolproof on its own.