Fathers should stick to just playing with their children as their efforts to look after them just end in arguments with their wives, a study claims.
Psychologists have found that couples have a stronger, more supportive relationship when the father spends more time playing with their child and less time feeding or bathing them.
The findings suggest that traditional roles work best and that a man who insists on helping with the baby care actually undermines his wife's efforts.
Professor Sarah Schoppe-Sullivan, at Ohio State University, co-author, said it was disappointing for people who believe mothers and fathers should share equally in the care of their children.
But she added that it shows that there is not just one way to share parenting duties.
"I don't think this means that for every family, a father being involved in caregiving is a bad thing," she said.
"But it is not the recipe for all couples
"You can certainly have a solid co-parenting relationship without sharing caregiving responsibilities equally."
Prof Schoppe-Sullivan and colleagues began with 112 couples who had a four-year-old child.
The couples first filled out questionnaires that asked how often they were involved in play activities with their children – such as giving them rides on their shoulders and backs – and how often they were involved in caregiving activities.
The researchers then observed the couple for 20 minutes while they helped their child in completing two tasks – drawing a picture of their family together and building a house out of a toy building set.
These tasks were designed to be slightly too difficult for preschool-age children and required the guidance of both parents, which gave the researchers the opportunity to detect how much the parents supported or undermined each other in their co-parenting.
The researchers looked for signs of supportive co-parenting, such as couples encouraging and co-operating with each other as they helped their child.
The team also looked for evidence of couples criticising each other's parenting or trying to "outdo" each other.
One year later, the couples returned to the laboratory and took part in a similar observed activity with their child.
The results showed that, in general, when fathers played more with their child at the beginning of the study, the couple showed more supportive co-parenting one year later.
However, when fathers said they participated more in caregiving, the couples showed lower levels of supportive co-parenting one year later.
The findings in the study remained the same even when the researchers compared dual and single-income families, and when they took into account a wide variety of other demographic factors such as father's education and work hours, family income, family size and the length of the couple's relationship.
The results fit into her other work, which has found that mothers can act as "gatekeepers" to their children, either fostering or restricting how much fathers are involved in caring.
"There might be some ambivalence on the part of mothers in allowing fathers to participate in day-to-day child care," she said.
"But fathers might be ambivalent too, and may not be happy about shouldering more of the caregiving. That may contribute to less supportive co-parenting."
The study appears in the journal of Developmental Psychology.