June 12, 2001 -- No woman is adultery-proof according to psychologist and author Dr. Bonnie Eaker Weil.

More than 50 percent of all married women, at some point, cheat on their mates, says Weil, so husbands should never be too cocky that their wife won't stray. "You have to be on the alert that at any moment you could lose your partner," she says.

20/20 and Men's Health Magazine chose three married women — a stay-at-home mom, a model and a production artist — to participate in a fidelity experiment.

They all say they are committed to their marriages and have never cheated on their husbands, but after examining their lifestyles, Weil says one of them is more likely than the others to commit adultery.

Weil's determination of who is most likely to cheat was based on the women's fidelity factors which are listed below. Her conclusion was that Erin, the stay-at-home mom whose husband regularly travels, is the most likely to be unfaithful. Click here to see that Weil's analysis was not a surprise to many ABCNEWS.com users. You can also watch video of the three women making their predictions.

Tonya Atkinson, 29 years old, is a production artist, and recently had a baby with her husband of four years. Experts say that passion wanes in almost all relationships in the first year after the birth of a child and Tonya admits that she and her husband don't spend as much time together as they used to. To get back in shape after the baby, Tonya has been spending a lot of time at the gym and says men are starting to notice her again. While she and her husband argue more now that they did before the baby, experts say respectful disagreements are healthy and show the passion in a relationship.

Erin Schmitt just turned 30. She's been married nine years and is a stay-at-home mom. Her husband travels for business, and is on the road at least two nights per week. Experts say a lonely wife may be susceptible to the advancements of another man. Erin's husband's frequent traveling made her the most susceptible to an affair according to Dr. Weil, and in fact, Erin has become friendly with a stay-at-home father who lives in the neighborhood. She says, however, her relationship with her husband still sizzles and when he's in town they enjoy their time together whether it's going out on romantic dates or just cuddling at home.

Natasha Pyle, a 29-year-old model, is a year and a half into her second marriage. She says she likes to flirt and gets a lot of attention from men. She and her husband enjoy going out dancing together and often have lunch together when she's not working. She says she is committed but admits she often holds grudges after arguments with her husband. Natasha was born in Russia where extramarital affairs are more common than in the United States.