Hi Michelle!
Just like what other members' suggestions, make sure lang to have a straight forward application which means you have all forms filled up properly and signed, supporting documents as needed esp the proof of relationship. If you will submit the application yourself, would suggest you write a good cover letter by saying a summary of how you and your husband completed all the forms with all supporting documents, etc.. You might want to mention your current condition as of writing of the letter and that your EDD or estimated due date is on __________. You might want to attach as well, a copy of pregnancy test from your doctor that shows the EDD. Basta any supporting documents that you think will satisfy them or they might ask, isama mo na
And as far as you know that they are already receiving everything that they might need and would like to see, that you hope or wish to have your husband's visa granted to him prior to your EDD.
Again, the above is only a suggestion if you will be doing and submitting the application yourself. Otherwise, you may hire an agent. Hiring an agent though does not mean the application will be done faster than those who chose to have their application done personally.
Good luck and take extra care esp with a very special little one that is now growing inside you