Hi Helen,
I had the exact same situation when I was pregnant with my second child. I had 5 months to the delivery date and IT happened (that was 18 years ago).
Without knowing all the details of the relationship and the occurence, it appears to me that your MIL is controlling, a bully and very insecure; give her an inch and she will take a mile (or more) kind of person.
Here is what happened with me. We had only been married for a few years; already had one child. When my husband's birthday rolled around I called to get a recipe for a dish that was his favorite. She said she didn't have any recipe's written down she just throws everything together and just goes by looks. "Besides," she said to me, "I (alot of emphasis on I) was going to make him supper for his birthday." I grit my teeth, took a deep breath and told her that while it was really nice of her to do that, she could send it home with him and we would eat it another night because I was going to make my husband supper and that is what we were going to eat that night. She then proceeded to tell me that she was HIS mother, said some pretty terrible things to me (left me in tears), and how dare I speak to her like that and treat her that way!
Now, most of you reading this will think that I should have just let her make him supper and not say a word. WRONG! This wasn't about supper; it was clearly about control. Everyone in the family NEVER stood up to this woman (even her husband). They always kept their mouth shut and then talked about it when she wasn't there and said she has always been that way and better to just leave her alone. Call me crazy and stupid but I wasn't going to live the rest of my life that way until she or I died. It also isn't the way God tells us how to handle things AND this was not the first time she had tried to get her way and I had always been extremely careful not to "rock the boat". I was polite and nice in EVERY way and she didn't like it because I was telling her "no".
The first was when we were getting married and making all the plans. I chose a pale pink color for the wedding; she didn't like that. She took me in the other room to show me a dress that she already had and told me how well it fit her and how much she loved that dress; along with the comment, "Peach is such a much prettier color don't you think?!" I knew then it wasn't going to be easy. At the age of 23 I truly didn't know how difficult it could get. I stood my ground and went with pink.
When my husband got home that night he already knew what had happened, see, he worked for his mother and father so when she hung up with me she, naturally, told him what I had done/said. He said that I needed to call her and apologize to his mother. The way I saw it I did nothing wrong and I surely wasn't going to apologize; she needed to be the one to apologize to me. I proceeded to tell my husband the truth about how it all happened. He still said that I needed to be the one to apologize because she never would and it would be better for everyone if I just did.
I wasn't going to do it; it wasn't the right thing to do. Everyone had always placated this woman and that wasn't right. So, I stood my ground. I also told my husband that he needed to talk to her. Remind her that he was married to me and not her. That he had a family now and his life didn't/doesn't revolve around his mama. She doesn't make decisions for us. Tell her that she could certainly make him something to eat for his birthday but that he was going to eat what I cooked for him for his birthday and that hers would be eaten another night and that she owed me an apology. Until she gave me that apology she was not going to be allowed in my house. I wouldn't go or be anywhere that she was (way too stressful) and she certainly wouldn't be allowed around me for the rest of my pregnancy and even when and after I had the baby. It was up to her if she wanted to see her next grandchild. And if he wanted to stick by his mother and be a mama's boy then he knew where the door was.
He had that conversation with his mama. I didn't speak to or hear from her for 4 months. As it got closer to the birth of our 2nd child, she realized I wasn't going to back down from the boundaries I had set and that she wasn't going to be allowed to treat me that way. She also realized that her son was going to stand by his wife. I had one month to go to the delivery date and was put on bed rest. She called and wanted to come see me to talk. She came over and she apologized. Keep in mind she apologized in her own way; she never came out and said she was sorry - but you have to be able to recognize what she was saying and how she was saying it.
My MIL had/has many issues. She thought, as some MIL's do, that she was losing her son and that he wouldn't love her as much anymore and that I wasn't good enough for her son etc. The more control she tried to have the more she lost her son.
I am a firm believer in setting boundaries and you teach people how to treat you. I am a Christian woman who is now 44 and have learned many things over my lifetime; lots of trial and error. Jesus had boundaries, and it is OK for you to have boundaries, too. Your husband needs to talk to his mother. She needs to realize that the two of you stand together and that he supports you. That his support for you doesn't mean he loves her any less. That she won't be allowed to come between the two of you and your family and that she will not be allowed to talk/treat you in that manner ever again or there will be consequences. You and your husband should have the consequences already figured out prior to him speaking with his mother. You must be committed to your decision and not waiver. If you waiver then you show her you don't mean what you say. Once she truly realizes you mean what you say you can then begin to have a relationship with her. YOU set the terms.
If I had to do it all over again I'd do it exactly the same way. Bottom line is it is up to you and your husband to decide how you are going to let your MIL treat you and your family. How you handle this situation will greatly effect the future of you and your husband's relationship, you and your MIL's relationship and your MIL's and children's relationship.
I didn't make my decision with the intent to get back at her. Yes, I was clearly hurt, however, my health and the baby's health was far more important than her feelings; during and after the pregnancy. Don't let her bully you into making a decision which will only contribute to additional stress being added. If you start to feel guilty it is a false sense of guilt. You already apologized for what you said and how you acted. You meant it. You shouldn't apologize again. She should have accepted your apology and been done with it.
You have to make decisions based upon other people's actions and inactions. She has chosen her path. You have to make decisions based upon her path because it has affected and will affect your life. There is absolutely nothing wrong with not allowing people to treat you like that (related or not). If you choose to let her back in you need to have clear, set boundaries.
I will say a prayer that God will give you guidance in this decision and things can be worked out. The birth of a child is a miraculous and wonderful event and it would be quite sad should your MIL choose not to be a part of it because she chooses not to change her behavior.
God bless you and your family,
Kim