Many doctors and midwives advise women who had a miscarriage to wait for two months before trying to conceive again. The main reasons for this are making sure that all relevant tissues have left the body, and that the menstrual cycle returned to normal. Some women will have irregular cycles for a while after miscarrying, just like they do after giving birth. When the date of conception is unclear, it is harder to determine the due date, and therefore harder to monitor whether a future pregnancy is developing normally.
I suffered multiple miscarriages, and personally I would like to advise women who want to try to get pregnant again after losing a pregnancy to have a check up with their healthcare provider, and to wait with trying to conceive again until they get the green light. I was actually surprised how little follow-up care I was offered each time after having a miscarriage. My appointment consisted of a transvaginal ultrasound to ensure there was no remaining fetal tissue, and a chat about how I was feeling mentally and physically. Some women would like to resume trying to conceive at the earliest opportunity, while others feel the need to wait longer. If you need to grieve for your lost baby, allow yourself that time. There are no rights and wrongs when it comes to conceiving after a loss, besides what you and your partner mutually agree upon.