Yep, this is my thought too. My best friend teaches 5th grade and she would totally have to have the "where do babies come from" talk with her class if she were pregnant. Of course we live in San Antonio where no one wants to talk about how you get pregnant then they act all horrified when their daughters end up pregnant when they're 14 years old.
Glad it worked out for you. I was going to suggest you just tell students if they ask and let the gossip do the rest...but your colleague got the ball rolling for you!