First of all C., CONGRATS on your beautiful miracle baby boy!!! My in-laws used to be the same way, and my husband (whom I love and adore) would not stand up to his family for me. I don't know if he was affraid to disrespect his family by saying something, although I was raised a different way. I respect those who earn my respect, I respect my elders until they give me a reason not to, and I speak up if I have something to say.
Only one time did I ever have to say something to his grandmother, she was mostly the problem from the begining. Aparently I wasn't good enough for her grand son, and therefore deserved to be talked down to constantly, and she would tell me literal untruths about him, in order to advance a divorce. It was a nightmare, and when I would tell my husband what she would say, his response is, she's an old woman, ignore her. UMMMM OK, not happening when we're around her enough for her to make my life miserable! One day I was supposed to meeting him after work, and he worked far enough away where it was easier to wait a few minutes at his grandma's house until he left work, and his grandmother started in on me. At that point, we'd been married about 1 year, and I had HAD IT!!! I've never talked to my elders like this, but I'd had enough, and I stood up for myself, I told her that I don't want to hear ONE MORE UGLY THING OUT OF HER MOUTH! At this point I was 7 months pregnant, and told her, if this is the way she is going to talk to me, I am certain that she will talk to me like that in front of our children, and therefor I can CERTAINLY MAKE IT POSSIBLE that she NEVER see them! I said some things that had been building up in my for the last year, and let her know exactly what I thought, and in the end, she was crying, begging me not to tell my husband what she's said. I'm not proud of making his grandmother cry, although, after that she never spoke a cross word to me, and we've been married for 10 yrs next month. She has always been respectful to me, as well as our children, and always gives me hugs, and love when I'm around.
It sounds like you have a similar Mother in Law, and in my opinion, if your husband doesn't take up for you, take up for yourself. You do NOT have to be treated that way, and keep in mind, you have the upper hand, you have a child she wants to be part of her life, let her know how you feel.
Everyone kept telling me, "don't rock the boat, or just deal with it, or tell your husband to say something" but when your husband WON'T say something then it's up to you to defend yourself against his family. If she gets angry at the moment, she'll get over it eventually, but she will gain a whole new respect for you in the process.
A.