An honest answer from a physician spouse....
There are several factors that come into play....for the most part, it seems that the physician spouse's career does take a backseat during medical school and residency...especially if you end up having children during that time.
The bottom line is that medical school and residency in particular are very demanding...it is just very, very hard as a spouse to be supportive of your partner who is embarking on such a demanding career at the same time that you are trying to move forward with your own career plans. That's not to say that it is impossible, and certainly there are spouses who do it.
While my husband was a resident, I did take some part-time classes and when he did his fellowship, I finished my MS in mol. bio...but it had high costs for our relationship. Also, I was not regarded as highly professionally because I was just not as flexible. I had small children and so instead of sitting around the lab I set things up and then came back at night to finish them up. I also had to comporomise in the types of classes that I took...I couldn't be killing myself for an advanced pchem course while my husband was working 100 hours a week and my children needed me. I often felt that during training there was only room for 1 'high-powered' career in the marriage...at least with the desire to raise happy children and have a strong marriage. When I was pushing the envelope trying to finish my MS we had very little stress-free time together. If I could go back and do it again, I would have not gone back to school at that time.
Another reason that it is difficult for the spouse to have a career is all of the relocating...moving for med school, residency, fellowship, post-training jobs....It's tough to finish your education or establish yourself as a professional if you are moving every few years...that would hold true for any working professional. I have had friends who are lawyers, PhD Cell biologists, Neuroscientists, etc...who have found themselves 'stuck' after the Match came out and they ended up in the middle of nowhere. I had a friend who went from 'publish or perish' to unemployment and a complete inability to find even a part-time teaching job at the local university. She ended up deciding that those 5 years of residency would just have to be the time for them to have their children....and they had 3! By the time that they were done with residency, she had not worked in science for 5 years.....not good if you are trying to be a career scientist.
Another friend of mine is an attorney with one child. Her husband is also in surgery and she has had to take a job that she considers to be a step down. On a couple of occasions she has said that a law clerk could be doing what she is doing...writing briefs for a judge. It certainly is not where she saw herself when she was in law school...but at the same time, with the demands of residency, the moving and being a mom...she knew something had to give. The resident can't leave the hospital if their child is sick or if she needs someone to pick him up from daycare....so she had to compromise professionally.
Of course, for every example that I've given you here, you can come up with someone who has gone to med school, vet school, dental school etc with their spouse and they've managed it all together. I guess a lot depends on the couple, the marriage and the timing of the schooling/moving, etc.
I've pretty much come to the conclusion (after 10 years of marriage and 8 years of residency/fellowship, etc) that it is possible as a woman to 'have it all'...just not all at once. We have spent many years focusing on my husband's career and getting him through training and established as a doc....when our children are older, my time will come...and I know that he will offer me the same support that I gave him. It took me a long time to find peace with this...but I really have.
kris