Slightly risque joke...

[mjr]

Three pregnant women are sitting in a waiting area of an OBGYN office. They strike up a conversation. The first lady says, "I'm having a boy, because when we conceived I was on bottom."

The second lady says, "Really? If that's the case, I'm having a girl, because when we conceived I was on top."

The third lady, not to be outdone, says, "Does that mean I'm having puppies?"

[Nunavut Pants]

The version I've heard has the three ladies as a brunette, a red-head and a blonde. The blonde, naturally, being the third. Except that she bursts into tears and wails, "I'm gonna have a puppy!!"