The bartender served a woman a glass of orange juice.  

The man sitting next to her, turned to her and said,

"This is a special day; I'm celebrating."

"I'm celebrating, too," she replied, clinking glasses with him.

"What are you celebrating?" he asked.

"For years I've been trying to have a child," she answered.  

"Today my gynecologist told me I'm pregnant!"

"Congratulations," the man said, lifting his glass."As it happens I'm a

chicken farmer, and for years all my hens were infertile.  

But today they're finally fertile."

"How did it happen?" asked the woman.

"I switched cocks." Said the man.

"What a coincidence," she replied.