Psychotherapist Esther Perel wrote her first book Mating in Captivity ten years ago. Her second book The State of Affairs: Rethinking Infidelity has just been published. She joins Jenni to hear from Woman's Hour listeners about the challenges they face keeping the sexual spark alive in a long-term relationship and to give advice based on 20 years experience of talking to couples .

Mismatched libidos, pain during intercourse, getting into a routine and what happens to desire when kids come along are some of the issues raised. Is it unrealistic to expect passion in a marriage? Why does the sex seem to go off even in the most loving relationships and does it really matter?

Presenter: Jenni Murray Producer: Erin Riley Reporter: Abigail Hollick.