How to Tell If Your Wife or Girlfriend Will Cheat, and How to Prevent It Beware the warning signs and stop her before she strays.

Jim was angry, upset, annoyed, and then angrier still. But most of all, he was perplexed. "I don't understand it," he said. "Things were going so well." The 32-year-old businessman's discovery that his wife of three years was having an  affair had sent his normal confidence soaring out the window. 
How could she do such a thing? And how could he not have known?

The answer, experts in the field of female infidelity say, is that he probably should have known. While cheating is about the worst thing that can happen in a relationship, it seldom occurs without warning. "Most affairs aren't sought, they `happen,' usually during a vulnerable time in the marriage," says New York state psychologist Don-David Lusterman, Ph.D., author of Infidelity: A Survival Guide. "If a man is conscious of what's going on in the relationship, it's a lot less likely."

It's hard to say how frequently married women cheat. Polls have had widely divergent results, showing that anywhere from 10 percent to 60 percent of the married female population will have an affair at some point-although marriage counselors say the lower end is more likely. But while most cheaters are still men (but not by much, actually), women are more likely than ever to be the ones who stray. According to Anthony DeLorenzo, a New Jersey-based investigator who specializes in checking out cheating spouses, the increasing number of opportunities means that the number of women who have affairs is rapidly climbing.

"With more women than ever in the workforce and on the Internet, their percentage is going up all the time. In our investigations, we follow about 68 percent males and 32 percent females, but the ratio will probably end up being 55 to 45," DeLorenzo says.

Do you know how likely it is that the sweetheart you married will have an affair? We've taken four scenarios to our experts to find out which ones are most apt to result in cuckoldry. Take a look, and learn how to prevent what happened to Jim from happening to you.