Mother-in-law present for birth

So my husband and I have been married for almost a year now and his sister-in-law just had a baby about 7 months ago. While we were visiting the hospital after the baby was born I was informed that his mother has been in the delivery room with each of her daughter-in-laws (3 daughters-in-law) for all of the grand kids births (9 times). His mom is a outspoken person and doesn't really know how to handle girls, she was raised by her dad and then had 4 boys, so I don't really blame her. My hubby and I are currently TTC. What worries me is how to tell his mom I won't want her in the room. It will be our first baby and I want it to just be my husband and I. My mom is completely fine with this and just extremely excited for us to give her a grand baby. His mom will not handle it as well, unfortunately, my hubby agrees that she will be upset. I married her baby and she does not do well with change. I do love her and don't want to hurt her. Any ideas on how to tell her gently now that it's become something that's "just done" in his family?