@cuteness20 How are you defining "bouncing back"? How long did you train prior to getting pregnant? What level are you "bouncing back" to? Was it endurance or strength based? The longer you trained something, the easier it is to recover prior levels. The higher level you are, the longer it might be to "fully" bounce back. And I believe that (fast-twitch) strength tends to come back a little faster / is lost less quickly.
I hear plenty of stories of moms who are sleep deprived. Sleep deprivation is not a good environment for your body to put on (muscle) weight.
I hear plenty of stories of moms who have PPD or PPA. This tends to affect all sorts of things, from diet to sleep to general stress/inflammation levels. Your body needs proper fuel to be able to recover / put on muscle weight. Higher, general inflammation levels similarly hurt your ability to "recover" after a work out and "bounce back".
Regaining old strength foundations (or whatever you do) requires consistency and commitment. Those can be hard with a newborn, especially depending on your partner, support system, job, lifestyle, plans, and even your mental capacity.
Any sort of training gains or "bouncing back" requires you to truly
rest between
consistent training sessions. Rest involves everything from physical rest (ie limiting actual physical movement / exertion outside of training sessions sufficiently) to high quality and sufficient quantities of sleep to eating healthy foods to eating
enough food to proper hydration. I also would not underestimate the "consistency" aspect: have you and your spouse worked out how you'll work consistent training in after you have a baby? If you're breastfeeding, have you worked out how you'll fit your training in? That may require pumping, or having baby nearby, or training for less time or closer near the baby.
My husband and I have very deliberately chosen a place to rent for our new life which will allow us to do most of our conditioning in our apartment (where we can pass baby back and forth between sets, or utilize an exersaucer/playpen/etc), in the apartment building (one of us can go down and 'take shifts'), downstairs at a public park with more equipment for conditioning (can babywear, exchange, or have a seat/area for baby, and it's less than 5 minutes to get back home if needed), we've worked out a schedule (short commutes included) for how we'll both attend classes on our own (outside of conditioning), and we've budgeted for using a sitter/daycare if we find we need it. We also have a pretty extensive meal prep routine we've used for the last year -- aimed at minimizing time necessary to cook, and having some meals prepped ahead of time or ones that require minimal time/effort -- that should make it easier to fuel up. I have a therapist ready and strategies for any potential PPD, but we also deliberately chose a location/lifestyle that optimizes our physical and mental health as much as possible.
Anyway, I have chronic illnesses that could very well flare up, and as first time parents we might (will!) find ourselves lost/stressed/sleep deprived. And there's a chance we could have a more "difficult" baby... so there might not be much "bouncing back", at least not right away. But I think that the most important thing to remember is to just do what you can, and to recognize that if this happens, it need only be a temporary phase you work through rather than as something that defines the rest of your life.
P.S. Some first time moms keep their pregnancy changes--and I sure hope I do, personally! My hips have grown
way wider, and my chest has expanded, aside from my breasts having already gotten bigger. It feels almost like a second puberty to me. With puberty, athletes in some sports say they have "different bodies" and sometimes even need to "become different athletes". That's not a bad thing, but it does require them to make changes in their approach and/or allow time to adjust. These changes will indeed require you to put on additional muscle and/or change your movement pattern a little bit--though this is going to be dependent on sport, with some more affected than others.