Your fertility, your ability to become pregnant, depends on if and when you ovulate. So the right question would be: "How soon after birth am I starting to ovulate again?"
There is no definitive answer to this question. Some women ovulate within a few weeks of giving birth and other women don’t ovulate for more than one year. If you are breastfeeding, prolactin could suppress ovulation to the point of infertility, but that only works for 1-2 months, and ovulation plus fertility can return within a few weeks of slowing your breastfeeding schedule.
Though obstetricians suggest waiting at least six weeks to have intercourse after delivery, some women have conceived in the first two to three weeks after giving birth.