Hey I was right where you are back in 2004 :) I was due with my first right during finals week the spring semester before my last fall semester of law school. (I actually had my mock trial final 5 hours before I was induced with DS!) I think like a PP said, it's how you deal with it emotionally. Right now decisions may seem easy, but when you have that little one in your arms, it's a WHOLE different story. It was very hard for me to leave him for any period of time. I, like you, got an internship (mine was with a construction law firm) for the summer. Thankfully, they totally understood (I had started that spring, and told them when I was around 16 weeks along) and I just started working again, like 20 hours a week around a month after he was born.
When I went back for the Fall Semester, I actually took him to all my classes with me and nursed in the back. He was EBF until 6 months :) The teachers were totally accommodating, especially since he wasn't a fussy baby. They thought it was pretty cool :) I kept the internship, but again, only worked 20 hours per week, during the fall semester. I interviewed in the fall and got a job, and by then he was older and more independent, and I felt more comfortable leaving him with my parents while I went to work full time.
FFwd to now? Started my own firm last year, and had twins 2 weeks ago, and we're all back in the office already :) AND I had a C-section ;) See what you have to look forward to?? We attorneys are tough bunch though right!?
Just to say it CAN be done, but you need to weigh those emotions you're going to be going through- Hopefully you can come to some arrangement so you don't have to work a full 40? That's my 2 cents though :) Feel free to PM me if you have any questions, I know it's tough, and you're very lucky that DH will be a SAHD! That's awesome!
Good luck mama!