A chicken farmer went into a local tavern and took a seat at the bar next to a woman patron and orders a glass of champagne. The woman perks up and says, "How about that? I just ordered a glass of champagne too!"

He turned to her and said, "What a coincidence." He continued, "This is a special day for me, I'm celebrating."

"This is a special day for me, too, and I'm also celebrating!" says the woman.

"What a coincidence" says the man. They clinked glasses and he asked, "What are you celebrating?"

"My husband and I have been trying to have a child. Today, my gynecologist told me I'm pregnant!"

"What a coincidence" says the man. "I'm a chicken farmer. For years all my hens were infertile, but today they're finally fertile."

"That's great!" says the woman, "How did your chickens become fertile?"

"I switched roosters," he replied.

"What a coincidence," she said.

How is the gynecologist so cock-sure she is pregnant?