As long as you wait until 6 weeks after delivery, any birth control method is safe even with breast feeding. Sex should be avoided until the 6 week postpartum check up. There is a risk of infection and of vaginal injury if a woman has sex before that time. There is also a risk of pregnancy. It is not uncommon to have patients come to the 6 week postpartum appointment and be pregnant. For an overview of available birth control options click here.
We generally wait 6 weeks to start birth control after delivery for 2 important reasons. Starting birth control prior to 6 weeks after having a baby can increase the risk of DVT, blood clot in the legs. Although rare, this can be extremely dangerous. There is also a concern that starting estrogen containing products prior to 6 weeks postpartum may affect the milk supply in breast feeding women.
There used to be a concern that estrogen containing products could decrease the milk supply. For this reason the “mini-pill” which is a progesterone only pill, was often given in the first 6 months after delivery. This pill has a much higher failure rate then the traditional birth control pills. It is now understood that estrogen containing pills do not decrease the milk supply. In my opinion, it is usually better to use the more effective combined birth control pills even while breast feeding.
Although it is safest to wait for 6 weeks after delivery to have sex, many people do not heed this advice. It is possible to get pregnant before 6 weeks postpartum. If you decide not to take the advice of the doctor, and you have sex before the 6 week postpartum visit, be sure to use condoms to protect against an unintended pregnancy.