Welcome, Daisy,
I, too, am a newbie to this site, and I can definitely relate to how you must be feeling right now, except for the pregnant part! ; )
I just lost my mother-in-law, who was a wonderful woman----but my mother is the MIL-From-Hell(and the bane of my existence), and I have witnessed firsthand what my poor brother and SIL have had to endure at the hands of my mother and Nsiblings.
If you would be interested in knowing more about my "story," you can go back to the index and look for the heading "Narcissistic Relatives." My first posting(with all of the details) is on the second page of that particular thread. But, suffice to say, I know what you're going through.
The other folks on this site have wonderful insight and suggestions, and I would most definitely concur that this HAS to come from your husband. I think that seeking counseling would go a long way in helping to fortify him for the battle that he will face if he decides to stand-up to her. If your hubby is a "self-starter" type who likes to read(as I am), there are a myriad of helpful books out there(which is a good start). Before I had even heard of Narcissistic Personality Disorder, I started my journey by reading the books "Toxic Parents"(by Susan Forward), "If You Had Controlling Parents," "Children of the Self-Absorbed" and a book written by Alice Miller whose title I forget(it may have something to do with the "Gifted Child," but it refers to children who learn early-on how to read the climate of their home life in order to appease unreasonable parents). I don't know if the other "posters" on this thread agree with my choice of literature, but there is a vast wealth of it out there. I just ordered the book "The Narcissistic Family"(I think that the author's last name is Pressman), as it came highly recommended.
One caveat: because your husband has spent a lifetime capitulating to this woman, she is used to getting her way, and if your H finds his "voice" to stand-up to her, she probably won't take him seriously right away. Worse yet, she will most likely pull-out all of the stops to try and preserve the status quo. In my experience, the more my poor brother dug his heels in(in the face of my Nparents and Nsiblings), the more desperate my family members have become to try and regain control, therefore, the more outrageous their behavior has become. So, in a nutshell, things in your situation may get a bit worse before they get better.
It would be wonderful if your MIL saw the error of her ways and did an about-face, but your husband has to "steel" himself to face the possibility that the only "solution" to this problem may be to sever all ties with his mother. She'll resist this, too, as that is what is happening in my family. Maybe my case is the absolute extreme(a lot of the more "veteran" post-ers on this site have told me that my family is off-the-charts psychotic), but I just returned from meeting with an attorney whose services I have decided to retain(my Nparents and Nsiblings' conduct has started to border on criminal).
I know that you have special needs to consider re: your health right now, but I would say that your husband is going to need you to be strong for him if he decides to slay this particular "dragon." I would put money on the fact that his Nmother will go ballistic if he decides to set more harsh boundaries, so he is going to need to have in you a very strong source of support, love, encouragement and(most importantly!) stability.
I don't know if you and your husband embrace any type of faith or spirituality, but I personally believe in a spiritual life after death, and a very wise woman told me to remember that my mother is/was nothing more than a channel through which I was brought into this world. I think about that when I am feeling down or inappropriately guilty about the situation in my family, and it puts my mother in better perspective where the "large picture" is concerned(she's not a deity, for crying out loud!). It might be something that you can share with your husband when Mommie Dearest starts pushing all of the familiar buttons.
I hope that this helps--either way, you're in a good place here. The other folks who post here are very supportive and insightful, so keep on posting---good luck!
promqueencasualty(pretty self-explanatory username!)