Wtf weds - rude!

What makes it ok for people to say to a pregnant woman, "you know what caused that, right?" I have heard that more times this pregnancy than ever. It pisses me off every time. Then to explain that this pregnancy was planned- not that it is any of their business, but now I feel obligated to explain. Regardless, is the situation of my womb your concern? Would you say that to any expectant mother? You don't know the circumstances behind the pregnancy, what if the woman was struggling with infertility? What if she had been the victim of rape?

And really wtf happened to a simple, "congratulations" ?