My In-Laws

So my husband&&I are ecstatic to be having another baby&&have only told his parents so far. We went to visit some of his family&&his mom got back in the car with a smile&&said, "I told them that piper's going to have a baby brother or sister." I just smiled&&said that's good but inside I was fuming. I wanted to make an announcement for the rest of the family after the ultrasound, but that's out now. I never told her that was the plan but I still figured that would be my story to tell. My husband isn't bothered by it, he said "my parents are so excited this is only their third grandbaby so let them tell people if they want." I love my mother in law, she really is the sweetest woman but I feel like I have every right to be upset. Opinions?