When to tell your in-laws you're expecting

I'm not pregnant yet, but my husband and I are ttc baby #1.  Although I love his parents, they're very overbearing. They have 6 grandkids, and they are their world.  I decided to tell my hubby's parents about my endometriosis a few years ago because they were always asking questions regarding when we were going to have kids, and their other kids all conceived their kids within a few months of getting married.  Since I told them about my endo, my mother in law has made passive comments such as, "did you cause it?", and has even told other people I am Barron and can't have kids (I never hinted to that, just expressed that conceiving MIGHT be difficult for me).  Anyways, I decided that when I do become pregnant, I don't want to tell them for awhile, especially since women with endo have a higher chance of miscarriages.  When is a "good" time to tell your in-laws you're expecting?  I don't want to offend them by waiting too long, but if I ever did miscarry I don't think they'd be the support I would want or need.  Thank you!