The reason that most doctors and other health care providers recommend that you abstain from sex for six weeks after child birth is that the damage to the cervix, uterus and vagina caused by childbirth put you at increased risk of infection. There is also a wound where the placenta has come away from the lining of the uterus, and there are some very good reasons to avoid introducing bacteria to the vagina. That means no sex, no tampons and no foreign objects in the vagina.
If you’ve had an episiotomy or have rectal or vaginal tearing, then you might even need to wait longer than the recommended six weeks for the wounds to heal. That’s because any strain may cause the wound to reopen, causing pain and possibly requiring more surgical intervention.
If you have not had any complications and you are healing well then the change in lochia (the bloody discharge you have after childbirth) from red to brown is usually a sign that healing is near complete, but that too can last anything from four to six weeks.
In order to be sure that it’s safe to have sex again you will need to have an internal exam and that’s why it’s usually recommended that you wait until after your six week post-natal check up, when your doctor or caregiver should be able to tell you if everything is okay.