I guess it depends on the profession a bit (I'm guessing vet?) but I've done something kinda similar. Certainly I bred before the *approved* moment, but hey, it's my life! And I don't regret it for a second.
I found my peers (i.e. young, predominantly female, starting out in career) tended to be a lot less supportive than the older set (who ultimately are the ones who employ me) who already have kids and appreciate the positives of them. One positive I've found with having kids early is that I never had the chance to pick up a whole lot of additional tasks that I would then have had to palm off to take leave. I'm going back 3 days a week in 2 weeks, and while I'm under no illusions that it's going to be full-on, I have good support and I'll be ok. And in a few years time, all my peers will be having their own kids, and mine will be old enough that I can step up and take up some of their slack then. They may not appreciate that now, but they will one day.
I don't know if that helped any, but I say ignore them. Congrats on the pregnancy and go live your life your way

If you want the career you'll make it work for you.