Mother over stepping boundaries

Okay ladies, so I need some help!

My mom and I have a really good relationship for once in our life and I would like to keep it that way. Recently I became pregnant with my second child and she has been crossing the line with my business. I haven’t told anybody I’m pregnant aside from those I want to know. Well recently I had to go to the hospital for abdominal pains. I had to let my mother know and have her come get my daughter from me and my husband because we would be several hours. I normally share everything with my mother, because I could trust her. Well me and my husband spent 9 1/2 hours total at the hospital and doctors office so we got home at 2:00am. The next morning I had to go back to my doctors office for a recheck and my mom took me. ( Husband had to work) My Mom admitted to me she told her coworker and her friend I was pregnant and in the hospital. Now, I didn’t want anybody to know I was at the hospital or why and she told them. She also took a picture of my ultrasound pics that I had on my kitchen counter and sent them to her co worker. I feel it’s an invasion of my privacy and I’m pretty pissed off about it.

How do I nicely ask her to back off and keep things to herself?

I really don’t want to ruin our relationship.