I'm all for having babies while training (started med school with 1, finished with 3 including one born Oct of MS4) but as a current intern I really can't think of a worse time to have a first baby than the months of July through June the year after you graduate. OK, maybe getting pregnant a few months into intern year would work. Maybe.
I agree with everyone else on this one - if your baby won't at least be 3-4 months old at the beginning of the year, I think there's a great chance you'll have regrets (or worse). And really, unless you're in a big program, having an intern out for 12 weeks at the beginning of the year would be very difficult and I think unfair to the program, the other interns, and yourself.
Of course you are right to worry about not conceiving right away, but you can always plan to wait 6-12 months if you don't. I know how hard it is to wait, but time will pass quickly!