Reality Check Counseling

People who have the need to control others often do so out of fear that they will be rejected. It sounds like you are less concerned about your MIL trying to take over than you are that your mother will feel intimidated by her and not get to enjoy the situation and experience. This is a place for boundaries. I'd tell my MIL that I want her there and throughout my child's life (if that is true). But, I'd point out that your desire to have her be a part of your child's life is not the same as needing her to tell you and everyone else what to do, how to feel and to predict the future.

So many times, people feel that setting personal boundaries is the same as hurting someone's feelings. The truth is, your needs and ability to express them in a respectful manner should NOT hurt anyone's feelings. If it does, that is because that person does not respect YOUR feelings and is not respectful of what you need. Their feelings aren't hurt, their pride may be. They might feel anxious, because you are taking away control that doesn't belong to them. But those issues are not for you to deal with or protect them from.

Be kind, but tell your MIL how it feels when she becomes controling. She will likely deny the behavior. Don't quibble over it. Say, "When you (insert specific behavior like, "boss people around") I feel (insert the actual emotion, like "frustrated, disappointed, hurt, etc.) and I need you to (insert the behavior you need her to engage in, instead). In this case, you could say, "When you said that you were better than my parents, I felt disrespected and protective of my mom. I'm concerned you will say or do something similar during the utrasound appointment and ruin the experience for my mom. I need you to promise to be respectful of me, my family and their role in the life of our unborn child. If you don't feel you can do that, I need for you to stay home and not participate in the appointment."

This will not be an easy conversation. She will probably be resistent to your request, and your husband may have trouble accepting your assertiveness, if he is not used to making his own needs known to his family. But, you will feel empowered, and she will have more respect for you, in the end.