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Children do not make for a happier marriage, according to a study that challenges some assumptions about what makes relationships tick.
The research, involving almost 4500 participants in the UK, found couples without children were more satisfied with their relationships than couples with kids.
It also found same-sex partners were happier than heterosexual couples, and unmarried couples with children were happier than parents who had tied the knot.
Researchers from the UK's Open University asked participants in an online survey to rate the quality of their relationships.
They found childless couples, both married and unmarried, were happier with both their relationships and their partners than couples with children.
Parents appeared to do less to maintain their relationships - such as talking or going out together - than couples without children. Heterosexual parents did worse than same-sex parents.
Of all groups, heterosexual parents were least likely to be there for each other, make time as a couple, pursue shared interests, say 'I love you' and talk openly with one another.
Fathers were less positive about their relationships and partners than childless men, but were as happy as childless men overall. Mothers were also less positive than childless women - but were significantly happier with their lives overall than any other group.
In the bedroom, fathers were twice as likely as mothers to list needs or expectations about sexual intimacy among the things they liked least about their relationships.
But the study also revealed a silver lining - relatively small gestures, such as saying thanks or making a cup of tea for a partner, were highly valued in relationships.
Sharing chores, cooking meals, saying 'I love you' and talking openly also rated highly.
Professor Garth Fletcher, who lectures on the psychology of close relationships at Victoria University of Wellington, said similar results about parents' relative relationship happiness had been found in previous studies.
"There's nothing unusual about that finding, even though people might find it a bit odd or unpalatable."
But the differences in happiness between couples with and without children were not huge, he said.
"So there's no need to go panicking and say, 'Oh, we better not have children, our relationship will go down the tubes'."
Relationship satisfaction tended to "ebb away" and passion decreased the longer people lived together, which could be exacerbated by having children, Professor Fletcher said.
Raising children was challenging and parents tended to have less time to send love notes, share romantic dinners or have a chat with their partner.
"They tend to get exhausted, so when they do have spare time, they sit there watching television."
Children also brought stresses, including economic stress, which could have a negative effect on relationships - but that did not mean parents did not have fulfilling relationships.
Other studies had suggested that in the long-term, especially later in life, people got added meaning from having successfully raised children, Professor Fletcher said.
RELATIONSHIP HAPPINESS - SURVEY RESULTS
* Men and women are equally satisfied with their relationships and life overall
* Middle aged men are less satisfied with their relationships than younger and older men; younger women are more satisfied than older women
* Childless men and women are more satisfied with their relationships than parents of both genders
* Fathers are equally as satisfied with life overall as childless men, and mothers are more satisfied than childless women