K.S.
I was working on my Internal Medicine Residency when my first son was born. I decided to take a one-year leave of absence. That kind of leave was possible because I was at such a large residency program and my absence didn't put any additional burden on my fellow residents. I switched rotations around during my pregnancy so that I had completed all my call before I delivered, and then didn't go back until the next "year" started the following June (my son was born in April). I just didn't know how I would balance the hours demanded by a residency with being the mother of a newborn, and I still feel it was the right decision for me. When I did go back the following year to finish up, my husband (a fellow at the time) and I hired a full-time nanny who ended up earning more than I brought home, but who was worth every penny spent.
Be warned: it was the hardest year of my life. My son was horribly colicky, my husband was still working ungodly hours, and going from respected, full-time-plus professional to a stay home mom was an earth-shattering experience for me. Looking back, it was the right thing for me to do, and I'm glad I did it, but I wish I had been better prepared for how I was going to feel.
Good luck and keep in touch!