By Chelsea Karnash

PHILADELPHIA (CBS) – If you’re planning a romantic dinner this Valentine’s Day, beware: your spouse might be stuck on the side dish.

According to “married dating site” AshleyMadison.com, Philadelphia experienced a surge in new membership sign ups during 2012, helping it unseat Chicago and earn the dubious designation of #8 on the list of “America’s Least Faithful Cities.”

In addition to cracking the top ten for the first time, the online cheating mecca also says Philadelphia is the city with the highest percentage of sign-ups on the weekend — only 71% of Philadelphia cheaters signed up to AshleyMadison.com during the week, as opposed to 86% of weekday sign-ups nationally.

And if you’re wondering why the City of Brotherly Love might be spreading a little too much love, AshleyMadison’s CEO Noel Biderman offers one theory.

“After a trying year with its professional sports franchises, it is not surprising to see Philly surge up the ranks of American infidelity,” Biderman says.

Ouch.

According to AshleyMadison, the most adulterous cities are:

1. Washington, D.C.
2. Austin, TX
3. Houston, TX
4. Miami, FL
5. Oklahoma City, OK
6. Richmond, VA
7. Boston, MA
8. Philadelphia, Pa.
9. Lincoln, NE
10. Phoenix, AZ