"IN theory, faithfulness is important in a marriage, but in practice, 50 or 60 per cent of married people have affairs." So says Dr Jack Dominian, a Greek born doctor and psychiatrist who will be addressing a Dublin conference on affairs this Thursday, organised by the Marriage Counselling Service.

There are, he explains, three different kinds of affairs: one night stands; short affairs that last a year or so; and ongoing, more serious affairs. The third variety is rare and tends to lead to the breakup of the marriage. But "the vast majority of affairs fall into the first two categories, and the intention is not to break up the marriage".

Dr Dominian, who founded the Marriage Research Centre (now called One on One) in Britain and was awarded an MBE in 1994 for, his services to marriage counselling, recommends that if all that has happened is a one night stand on a business trip, it is more sensible not to reveal the affair to your spouse: "There is no point, it will only cause unnecessary hurt."

Nevertheless, for better or for worse, people usually tell their spouses about the affair; either directly, or by leaving clues. "Men like to get it off their chest. Once they have confessed they feel less guilty," says Dr Dominian. Women broach the subject for a different reason: "Women want to have a constructive conversation about why the affair has taken place and how the problem can be solved."

Men are rarely prepared for "the emotional pain" their confession unleashes in their wives: "Most men just admit they've had an affair without leaving any time to talk it through with their wives. They think that if they confess and are contrite, that their responsibility is over. They don't realise that their responsibility has only bust begun."

Dr Dominian will tell the conference, to be held at the Marino Institute, Griffith Avenue, that although the typical image of the adulterer is that of a man, an increasing number of married women are having affairs too, partly because more women are working outside the home.

Men and women have affairs for different reasons: "Men tend to have affairs just for fun. Women have them for emotional reasons. They could be feeling powerless, depressed or put down. An affair will boost the woman's morale."

A particularly testing time is when the couple's first child is born: 15 per cent of men who have affairs do so at this time: "The arrival of the first baby is much more stressful than people imagine.

"The husband must understand that the first six months of the baby's life are particularly tiring and stressful for the mother. She needs his support."

The time of pregnancy and birth is a difficult one for the father, says Dr Dominian: "He can feel excluded by the intimate link between the mother and the child."

Other stressful times can cause a person to have an affair, from illness to hitting middle age: "People feel they need to revive their spirits, and having an affair is one way of doing this." A person can drift into an affair if his or her sexual and/or emotional needs are not being met within the marriage", he adds.

"Marriages can survive affairs," believes Dr Dominian: "There is the shock and the pain of discovering that your partner is having or has had an affair. But afterwards, if trust can be re established, the marriage can survive."

He thinks that human beings are by nature, mostly monogamous: "We are programmed to spend our adult lives in a one to one love relationship." He has never known the concept of an "open marriage" to work in practice: "In reality, jealousy is never far away."

The ideal scenario, he suggests, is to stay married to the same person: "Marital breakdown is bad for the couple and bad for the children. And, moral reasons apart, there is evidence to show that once the marriage breaks up, any subsequent relationships become more difficult to sustain." He blames our unreasonable expectations of marriage for the fact that marital breakdown is now so widespread: "We have massive expectations of marriage. People don't realise that the initial falling in love is not sustainable, and that they will have to work at the relationship.

"I have observed that people's expectations shape what happens to the marriage. Because of women's emancipation, women's expectations are now very high, especially in the emotional realm, and men are not very good in this area."

He adds quickly that he is not against women's emancipation, but that it is important for men to take more cognisance of it.

"The church, which is dominated by men, is going to have to take much more seriously the area of marriage and personal relationships in order to be able to give proper guidance to the people," says Dr Dominian, adding that he can see a time when priests will be allowed to marry for this very reason.