Do married married women fantasize about having another man's baby?

My wife and I dated for 5 years, married for 7, and have children ages 4 and 2 (I got a vasectomy with mutual agreement after our 2nd child).She's always remained in very close contact with her ex boyfriend (he's now married with 2 kids).He moved several hundreds away for a good job about 2 months before we started dating- we were both very experienced with other people prior to meeting.Lately they've been talking on the cell phone late at night after I'm asleep and I've noticed that her vibrator has changed positions several times, so I ume she is using that either during or after their conversations.However, instead of being mad or jealous, I've actually found it to be exciting.I've asked my wife about the vibrator and she's denied it; however, during our lovemaking, she often role plays about having another man's baby and has big "O's" this way.Do women fantasize often about this?Would you ignore this or would you be concerned about infidelity in our relationship?