ANY THOUGHT WOULD BE NICE!!!

I'm worried what my parents in laws reaction is going to be when we tell them I'm pregnant because they are really stuck up and his mother doesn't like me! She talks to me like im 4. All my family will be happy for me and his brother and his wife but his parents won't. What do I do? How do we break the news? And how should I react or what do I say if they start on me?we might have his brother and SIL with us when we say (we will tell them first) I'm 19 he's 20. I don't need a telling off so keep that to yourself.