Quoting Squeaky McGee:" It takes about 6 weeks for the uterus to heal, hence the 6 week checkup. There's still a risk of a infection and pregnancy."
Idk I just went by what my OB said. Of course we used protection, for birth control reasons and to keep his "stuff" out of there since I still was worried about infections. But I was also exclusively breastfeeding every 2-3 hours which I know is not foolproof but it does raise the % so add that with a condom and its close enough to 100%
"Generally, it's considered safe to start having sex again once your postpartum bleeding, or lochia, has stopped. This indicates that your uterus has healed and sex is no longer considered an infection risk. If you're still bleeding, it could mean that your cervix is still open, leaving your uterus vulnerable to bacteria."