For years, having children was widely regarded as a cementing factor in a marriage. This was a view borne out by statistics; for those who married in the 1950s, each additional child reduced the chance of divorce by 16 per cent.
But not any more. According to a study due to be published later this year, being a parent now increases the risk of divorce. Research at Oxford and Limerick universities has found that by the 1990s, each additional child raised the risk by 37 per cent. Tak Wing Chan, a sociology lecturer at the University of Oxford and co- author of the study, said: "Most of our results are consistent with conventional understanding of the dynamics of family and divorce, but we found that in the last two decades the effect of children on divorce has changed. It used to be a stabilising factor in marriage, but now it increases divorce risk."
The change cannot be explained by the growth of non-conventional families. When families with step, adopted or fostered children were dropped from the analysis, the results were essentially the same. Chan said the reasons were not clear, but that the risk was most pronounced in low-income households.
Elizabeth Martyn, the author of Baby Shock! Your Relationship Survival Guide, says that prospective parents are often unaware that having children would profoundly affect their lives. "Ninety-nine per cent of parents adore their children. What they often find they don't like so much is the actual business of being a parent, and the level of responsibility and the changes that it makes to their lives. That's the shock, it's not the baby itself. It's more: `God, I wished I'd known what it was going to be like.'"
Denise Knowles, a Relate counsellor, puts it more starkly: "When you become a parent you almost have to put your life on hold. If you are not prepared to do that, then you are not being realistic."
Many parents find that time becomes a precious commodity. For some, the answer may be for one partner to give up work, although such a change in roles can lead to other sources of conflict. The stay-at-home parent may feel a lack of identity, while the sole breadwinner can feel under tremendous pressure to provide for the family while juggling the demands coming from both home and the office.
Women often find themselves doing most of the domestic chores, which can lead to arguments. Kate, a 38-year-old mother of two who lives in London, said: "As a card-carrying feminist, if someone had told me how much having children would polarise the gender roles in our relationship, I would never have believed them.
"Many women find themselves at home at least for a few months when a baby arrives, while their partner goes out to work. Most of the baby chores inevitably fall to the mother, and from then it can be very hard for the father, even with the best of intentions, to get a handle on what needs doing and when. The woman can easily become `the boss' of the domestic stuff, and often still bears most of the responsibility when she returns to work, which is a source of tension. It happened to me - and I was a Greenham woman, for God's sake. …