Ultrasound Bookmark

I found this in a young adult book at my library. I wonder if the person who left it was using it as a bookmark and forgot it (which still begs the question why you’d use an ultrasound picture of a baby for a bookmark, but to each their own, right?), or if they left it deliberately, and whether the person who left the picture was one of the parents or just a relative or friend. I’d guess it was a teenager, because of the section the book was in, but you never know. I just wonder if there’s going to be one less picture in a kid’s baby book because someone forgot.