I went into school having been married for 3.5 years and no kids (still no kids). I personally can say that school has been very trying on my marriage. To be perfectly honest, if you are giving 85%-100% to school (which I have done since I consider this my job and the only training I am going to get to prepare me for residency) it is difficult to adequately give your spouse the time they deserve too. I am pretty involved with school organizations/activities as well, so this also takes part of my time, however it has helped me make contacts in the profession and I have learned a lot outside of school. My husband supports me in my studies and additional activities which is necessary. If you have a spouse that doesn't support you or doesn't know what they are in for, then it will be extremely difficult. I believe you need to make the decision about how involved you want to be in school, how much time you are willing to dedicate to studying (which kind of equates to what kind of grades are you willing to settle for, b/c I know people in school who study less so they can be with their families and are happy with B's and C's) and how much time is necessary to spend with your significant other. Not to be all counselorish...but your first year of marriage is supposed to be where you are both bonding together etc etc....I don't know when you planned on getting married, but I can only imagine how difficult it would be to really spend a decent amount of time with your new bride in your first year of school. It is a pretty stressful time, esp the first semester...depending on the school the curriculum may be quite hard (I know des moines has a hard first year and their 2nd year is supposedly easier, my school has kind of hard 2nd semester 1st year and hard all 2nd year).
As ldsrmdude said there could be a support system for your wife with other wives, however at my school that is just with other lds members...not for any other students who are not lds (i mean i am not saying that they would not accept your wife ( I am sure they would) I am just saying I know they often do those activities amongst themselves). There really isn't anything at my school to connect other spouses together..we have a club called "support our spouses" but they don't do much. Luckily my husband works and has met friends there.
I am not trying to deter you from getting married, just want you to think of everything and have a good talk with your gf before if you haven't. I told my husband this beforehand about how I would be really busy, but I don't think we expected this.