Buy, buy, buy! The rates are really low right now. Of course, it's like playing the stock market. You never know what's going to happen. We just bought and are moving into our new house this weekend!! Yep, I have a month to go. You really don't want to move while with a baby. There is nothing worse than feeling unsettled when you are expecting a little one. I wouldn't do that to yourself. The nesting thing is very very real. If you knew you would be renting for a longer period of time, had some debt you really needed to get paid down, didn't know where you really wanted to live or live in an area that is pretty expensive...then I would say wait. Sometimes it is better to wait because with baby, comes additional expenses. It all depends on your situation.
We were going to rent a few more months and use our lower rent to pay off our debts. We decided to buy because of the market right now (complete buyers market - antsy sellers), very low interest rates, and my insane nesting craze that I am currently experiencing! Plus, we haven't been that stable for a while and we really long for stability. Buying was the right move for us.
Good luck.