The local doctor, a married man, had to leave his home in the US and go over to Germany for a medical conference. While at the conference, the doctor met up with a beautiful woman and (for one night) forgot his wedding vows.

A month or so after his return to the US, he recieves a call from the German lady. "I'm pregnant." Shocked and angered he told her not to call again. She protested, "When the time comes, don't you even want to know if you have a son or daughter?" He decides to give her his home address and tells her to send a postcard (no return address of course) with a just a few words to hint at the sex of the baby.

Several months later, his wife calls him. "Honey, you recieved the strangest postcard from Germany in the mail today."
"Really? What's it say?"

"Sauerkraut, sauerkraut, sauerkraut. Two with weiners, one without."