The question here may be about what would happen if a man took birth control pills, but a more important question might be why a man would take birth control pills in the first place. Let's answer the what, and then take a brief look at the why.
But first, a bit of standard advice: Before taking any medication, consult a physician who can recommend the best course of treatment for you and your symptoms or condition.
Birth control pills contain two hormones, estrogen and progestin, that women's bodies produce naturally. When taken in the form of birth control pills, these hormones will regulate a woman's menstrual cycle and keep an egg from implanting in her uterus, thus keeping her from becoming pregnant. These hormones are also made in smaller amounts in men's bodies. Estrogen is used in sperm development, and progestin makes testosterone [source: Planned Parenthood].
If a man took just one or two birth control pills, nothing would happen. There is not enough of either hormone to throw a man's body out of balance with just a couple of pills. However, if a man took birth control pills on a regular basis over an extended period of time, his breasts might grow larger, his testicles might shrink, and his sex drive and amount of facial hair might decrease. Higher levels of estrogen also increase the risk of an enlarged prostate and prostate cancer. On the upside, birth control pills may help protect against heart attacks, but that possibility is too iffy to be a good reason for a man to start taking them [source: Maine].
Now for just a bit about why a man may want to take them. Some may think that taking birth control pills can help a man become more feminine. This is not the case. If femininity is the goal, there are safer and more effective ways to achieve the result. The first might be adopting more feminine behaviors and dress. A man can also look for clubs and groups of people who identify in a similar way and that offer support, friendship and activities to people who are exploring gender identity. Find a therapist or counselor who can help you understand the reasons you're exploring femininity. Seeing a therapist is often a required step before hormone therapy can begin [source: Go Ask Alice].
So if you're a man considering taking birth control pills, stop. Look at the reasons for your curiosity and what you hope to achieve. Next, find someone — a doctor or therapist — who can help you figure out the best way to reach your goals.