Some people are itching to jump back in, and others choose to steer clear for a while. It is recommended to wait at least 6 weeks regardless of how you gave birth. The risk of infection, trauma to the area and the fertility rate.
When you've just given birth, your cervix doesn't close straight away making it easier for foreign bacteria and germs to enter the uterus. You also have an open wound where your placenta was attached to the uterus wall. If an infection occurs, it can very quickly turn to sepsis requiring urgent medical care and likely an IV of antibiotics. If you have had tearing or an episiotomy you may need to wait longer until fully healed. Some women experience dryness to their vagina which can cause friction irritating any trauma to the area. This is most commonly seen in women who breastfeed due to the change in hormones. It is recommended to use some form of added lubrication to prevent friction.
After birth you are considered extremely fertile, although breastfeeding does provide contraception it is not a fool proof method. You can begin ovulating without having a returned period. Contraception will be discussed at your 6-week check-up. When breastfeeding you and only use single hormone contraceptives or barrier contraceptives. These include IUD's, nexplanon, depo injection and the mini pill or condoms, diaphragm, cervical cap and sponge.
For more information on contraceptives follow the link below.
For all the women worried about the tightness of the vagina post birth, the vagina is a muscle and will return to the same size within 6 months post birth. You can also do kegal exercises to strengthen the pelvic floor muscles.