I'd say go for it! The only reason I'm waiting until June to start trying is because we are going to the Gold Coast and pregnant women can't go on the rides. (I've obviously got my priorities right! )
But if it wasn't for our trip in June, I'd be trying this month. Even if it did mean having a January baby. As long as your house (and/or work) has air con to get you through the stinking hot months while you are heavily pregnant, I think you'll be okay.