Telling narc MIL we're pregnant?

Looking to hear from others about this. My husband and I have been married 8.5 years, together for nearly 11 and are expecting our first (rainbow baby!). I'm 38 and husband is 39, so I'm sure no one is expecting it. We have not told my husband's family and likely won't for several months. My husband doesn't even want to say anything until after the birth! I'm sort of encouraging him to say something sooner since I think it will be worse if he doesn't. This would also be the first grandchild- on both sides. He is NC with his mother and LC with his sister (a mini version of the mom), and has some more contact with his Dad and brother. The last few times he's spoken with his mother (funerals) she just screamed at him- literally. So he's worried about getting endless texts, phone calls, emails, etc from his mom about this pregnancy. She doesn't contact him now so i don't think it would be different. But I think not telling them till the birth would make them more angry and would hinder the "relationship" with his family more. Also, they don't visit us and we don't visit them. Too stressful. And I likely have relationship PTSD after dealing with his family earlier in our marriage (according to a therapist), so he's also concerned about the effect on me. Has anyone been through this?