Dealing with an invasion of privacy during my first pregnancy

I’m currently 10 weeks pregnant and work as a first-grade teacher. Although I don’t have a noticeable baby bump yet, all of a sudden one day I became significantly bloated. While I was letting my first graders into class one morning, a student’s mother approached me, touched my stomach, and asked, ‘Is this what I think it is?’ right in front of my students. I was taken aback and didn’t know how to respond, so I just laughed it off. Fortunately, I don’t think my first graders caught on, but I was really offended by her intrusion and the personal nature of her question.

The next day, she came into my classroom when I was alone to discuss something else and then said, ‘By the way, congratulations! How far along are you?’ without any confirmation from me. I was again shocked and upset that she would make such an assumption. This is my first pregnancy, and my husband and I haven’t even told our families yet, so her behavior felt like a violation of my privacy. I had to lie and tell her I wasn’t pregnant, and she just apologized with a casual ‘my bad’ reaction. I can’t talk to anyone about this except my husband, so I needed to vent here. Why do people think it’s acceptable to invade someone’s personal space like this?