If she is pursuing a demanding specialty, consider having your kids while she's a resident; I've known a few people that did it and while it's hard, it can be the lesser of evils. Fellowship is just as hard - maybe even harder - than residency, and when you're practicing she likely won't be eligible for maternity leave initially and can face pressure from the group to keep on working (otherwise someone else might end up having those brutal all-weekend calls back-to-back... not a good way for the new person to make themselves popular with their group).

Of course, it's a different story if she will be in a more sane line of work, such as hospitalist, ER doc, etc.