My pregnant wife won’t have with me, but I found out that she has bought a vibrator!?

My wife has been pregnant for 30 weeks or so, and whenever I mention having , she tells me to go away. She seems to want me to think that she is really turned off by the whole idea, but the other day while helping her out with the things around the house; I found a vibrator in the drawer. Now I WAS NOT snooping, but I was very surprised. I decided that it would be best not to mention it, but I have noticed that it gets used almost every day while I am work. The whole idea really turns me on, but how do I bring up the subject without her thinking that I have been spying on her?