I just had a baby during February of my fourth year and thought the timing was great. I got about 3 months off with him, and am now finishing one more rotation before graduation. One reason the timing was so good though is that my husband is also a fourth year medical student so we staggered our vacations and he is home now with the baby. My son will be about 4 1/2 months when I start internship which isn't ideal probably, but at least he sleeps 6-8 hours at night right now and it can only get better!
Interviewing while pregnant wasn't bad at all and I think it was preferable to interviewing with a newborn. I could do it now that he's about 3 months, but the first few months were rough. I can't imagine leaving him for 1-3 days at a time to travel. I didn't have to do anythign different while pregnant and I was interviewing up until 33 weeks! It just got uncomfortable to drive for so many hours
