Her daughter is pregnant but she did not sleep with anyone. But How ?

The doctor walks over to the window and just stares out of it.
A few moments later, the mother says, “Is there something wrong out there, doctor?”
The doctor replies, “No, not really. It’s just that the last time something like this happened, a star appeared in the East and three wise men came over the hill. I’ll be damned if I’m going to miss it this time!”