I was planning for a summer baby and I'm getting a Christmas one lol :)
I think the only reason to worry about what month to do a IVF is if there is a month you don't want your baby to be born... ie: around Thanksgiving, Christmas...ect. Other than that... it really doesn't matter.
Successful IVFs are done in every month of the year. (So, for that matter, are IVFs that don't succeed.) And I'm not talking about small numbers, there are hundreds of thousands of IVF babies presently in the world. (And tons of records are kept. If there was some month that didn't work, it would have been noted in the research!) Try your IVF in a month that works for you. Please also keep in mind that babies aren't always born on their due date, so if you are trying to plan a month for the baby to be burn, don't plan *too* hard. :)