Less than 20 years ago, most American married couples viewed children as a very important ingredient for a happy marriage. But that's no longer the case, according to a recent survey by the Pew Research Center. Having children has fallen to eighth on a list of nine keys to happiness in marriage, way behind what is now considered more important, such as sharing household chores and being faithful.

Andy and Trudy Ross have been married for around 10 years. They told NBC news they agree with the 99 percent of American couples in the survey that fidelity is the number one factor in a happy marriage. That's followed by a good sexual relationship, adequate income, decent housing and - says Trudy Ross - sharing household chores.

"That was almost a deal breaker in our own relationship, you know, when one person is doing more in the house than the other," Trudy says.

Having children, once listed among the top five keys to a happy marriage, has now dropped to number eight, considered important by only 41 percent of the couples surveyed.

"I'm so happy we have kids," Trudy says. "But it compounds all those other things on the list, faithfulness, having a good sex life or sharing the household chores."

Psychologist Dale Atkins says Americans think differently about marriage, especially about the role of children in marriage, than they did 15 or 20 years ago. "The relationship with children is very, very important to each individual parent and to the couple," she says. But the relationship that they have with each other is very, very important to making their life enriched."

Atkins says having children has become a choice. "You can choose to have children and not to be married," she says. "You can choose to live with another person and not to be married. And these choices are also encouraging people to say, 'Okay, now when I get married, I'm getting married for different kinds of reasons.'"

That's why Atkins says she is not surprised that many Americans consider sharing household chores more important to a happy marriage than having kids.

"There are so many stresses, very often, with two-career couples," she says. "And raising children adds more stress. So, if you feel you have a partner, and you feel you can depend on someone to share the everyday life, you are feeling more relaxed and more connected. And then you'll feel as if you have someone who you can talk with about issues having to do with children. "

Atkins says, that's missing when couples don't share household chores, "because one person is very tired, one person is resentful, and then they're not connected with raising their children."

The results of the survey don't mean American married couples are not interested in having children. According to psychotherapist Keith Ablow, they are looking for a marriage that helps them become happier and more fulfilled individuals.

"It's really about two loving people creating a context in which they can raise children happily," he says, "and people are taking different paths."

Both Ablow and Atkins consider the survey results good news for American couples.

"There is another silver lining, which is this: if you can improve a marriage by simply saying 'Listen, I think you should take the trash out.' I think that's easier than saying, 'Listen, I think we gotta have a third kid here in order to restore some sort of balance.'"

"I totally agree," Atkins says. "We can help people develop the skills to get along better as couples. One of these things is to be more open and share what needs to be done around the house and to care for extended family members together."

Psychologist Dale Atkins says when married couples are happier individuals and more considerate partners, they are more likely to become better parents. Through that solid, loving relationship, she says, they can pass on to their children some of the most important secrets to a happy marriage.