First off, soapbox, planning is one thing, but it may not happen exactly when you want and you may have trouble. Its ok. Just keep that in mind.
Okay, now that thats over with - Ive met one resident who had a baby ?2PD year and then again during residency. She had a lot of family support (grandmom watched the babies?) and she sacrificed a lot of time away from the babies (onbviously) but she made it work.
I got pregnant during 3PD year and had my son smack dab in the middle of rotations. I scheduled my month off on my due date, and worked double time on the rotation before he was due so that I had the last half of the 4th week off (luckily they were very flexible). I presented on tuesday, did my last day wednesday, had my c-section that friday (not preferred, he was breech). I spent 4 weeks at home with him then began my new rotations. My husband stayed home for 12 weeks (someone needs to stay home for that long.... a 3 month old baby is such a different animal than a 6 weeker). Kid did daycare at 3 months, has been ever since (but I work PT so he only goes a few days a week).
I had several types of rotations and If I had been on my hardest rotation post baby I probably wouldnt have made it. I had challenging rotations, though, and I made it work. Lots of delerious tiredness, lots of finding reliable rooms to pump in, lots of guilt, but youll have that regardless. Youll need a supportive husband, a thick skin, and a lot of naps.
I wouldnt change a thing.