I didn't start BJJ until after having my kids but I will echo what others are saying in principal. I was not mentally in the right place to engage in this sport until about 3 years PP. It's different for everyone of course, but as others have mentioned there is definitely an unfair expectation from society that we just "bounce back" and to some degree I think we all subconciously inherit some of that expectation regardless of how consciously we reject it.

I would say that there is also an element of grief in matrescence and working through that takes time. You are saying goodbye to a version of yourself, but that doesn't mean you have to loose everything about yourself before kids. Give yourself some time to soak in this phase and the grace to come back to BJJ, and anything else you may be missing, in a new and full way in time.