Thanks for your reply. That's what I thought I should do. I am a British citizen, so he will gain citizenship through me. I intend on applying for a British passport for him after he is born. At the time of our application we won't have a child, so it isn't as if I am lying. When we enter the UK the border patrol officer isn't going to know if I stated we have a child or not, right?
I have written a letter for my husband's application explaining that we wanted to move to the UK because we are expecting a child, but maybe it would be best to omit that part?