What is meant by the phrase "Oh, Matron!", when used as an exclamation?

I have a friend who often mutters, “Oh, Matron!” in a groaning, cheesy voice.

I feel really dumb for not understanding what this means. The web definition I found when I searched says a matron is married woman with kids. It does not allude to the meaning of this phrase when used like this though. I am not married nor do I have children. Am I a matron?