What will happen is they will ask you about all previous pregnancies and you will need to tell them. But what you can do is when you pee in the cup let them know about it and ask not to talk about it in front of him. But honestly maybe you should be honest with him about it. But I've had one and they never brought it up after that one time they asked
You could call ahead of time and tell them not to mention it. You never know, they could slip up unless you make it clear. Especially because they ask you questions about previous pregnancies for their own information along with other medical history questions.
honesty is very important in a relationship but if You really don't want him to find out I would say somthing to you midwife. When you go in to have your baby if your going to a hospital they always will ask how many pregnancies you have had and how long you carried each baby for. I got asked multiple times by different nurses even after they wrote it on my chart. They ask for both of my girls.