how to announce when sister in law had miscarriage

I think you should tell her privately first and give her the option of not being present during the big announcement. 

I think the best way is to tell her privately first.  this is a little different but one of my coworkers (who I was close to), got pregnant right after me. I had no idea but I ended up miscarrying. She found out about my miscarriage so before the news came out that she was pregnant, she took me to lunch and told me that she was pregnant. It meant a lot that she made it a private moment knowing I was still grieving.  I think telling her privately and giving her the chance to absorb the new before making a big announcement, is the most respectful way to handle it. 

As someone who has had multiple miscarriages it's hard but I agree with enjoying your pregnancy to the fullest. It will be hard for her but she wil be happy for you. Just try to be understanding of her. I would let her know first it will help that she will have time to come to terms with feelings. But let her know you want to tell everyone else so don't let it leak.

I'd tell her before you announce! Just the two of you alone! That way if it brings up any emotions she won't have to deal with it in front of a ton of people. 

I absolutely hated when people kept pregnancy and baby related things away from me because of miscarriages. Like I had some sort of disease.  Someone once told me I didn't invite you to the baby shower because I new you would be upset.  I hated it and still do. It's hard yes. But I was still happy for whoever was pregnant.  I would never wish anyone to have to go threw what my husband and I did for so many years. Everyone would tell my mom pregnancy announcements and my mom would tell me.  Made me feel horrible. In my opinion I wouldn't leave her out of the way you announce and I wouldn't do less because of it.  She will have her time one day.   I went threw 4 traumatic miscarriages ( normal, chemical, ruptured ectopic and miscarriage medically induced at 12 weeks) never thought I would have my time. Here I am 27 weeks pregnant with a healthy baby boy. 

Maybe talk to her first and tell her you understand she's still hurting and you don't want to make anything harder for her but you do want to include her as long as she wants to take an active part in things. If she even needs a moment to just breathe and step away you're okay with it and you're still there for her when she needs you to be. Miscarriage is very hard and while everybody around those who have suffered one are able to move on and be very happy it's harder for them to move on completely. It'll take time for her to heal but seeing that you still want to be there for her can help her more than you see. Don't take away from your happy news at all but keep in mind that while she's happy for you she will have her moments of envy and grief while trying to hide it behind a happy mask. 

I have had a miscarriage myself, and as hard as it is seeing others getting pregnant... you just have to suck it up and be happy for other people. Her time will come but in the meantime, why should you have to hide that you're excited cause you're expecting? You don't have to flaunt it but you should be able to celebrate with family.

I would have been devastated if someone had done a huge family announcement, I'm just being honest! My brother and sister In law also had a miscarriage and like you, they were grieving when I felt pregnant. For that reason, we did fun announcements for our parents. But for everyone else we went and visited them seperately. At least that way my brother didn't have to pretend to be happy in front of everyone, or for very long xx 

Honestly,I would tell everyone separately. Like send a picture or card or something. If you tell everyone at the same time with her there, she may look happy for you but it may make her really sad since she may still be grieving. Or you could just talk to her alone before everyone. Tell her you wanted to respect her feelings and didn't want her to be uncomfortable. She may push for you to tell everyone then, but she'll be happy you spared her feelings. Good luck