Congratulations. It is great that you are thinking ahead, and using this time to try to help others in your community in a similar position.
ACE does offer a specialty cert. in pre and post natal. They have good name recognition, and my experience of doing several of their certs. is that they are very informative and helpful.
I see that you have a personal training certification, but do not seem to have one for group fitness“. Do you have experience with groups? If not, you might want to get your group fit certification even before doing the specialty. During my years in the industry I have done both, and I feel there are real differences in approaching a group. Although, as a lot of trainers do small groups, you might have enough experience in differentiating and group dynamics, that you will find doing the specialty is enough.
Good luck, and be well.