Researchers found that when a new mother was anxious about her parenting abilities, she and her partner tended to be less satisfied with their sex life, compared to other first-time parents.
For men, it was different: Only their partners' stress levels -- and not their own -- seemed to affect their views on their sex life.
It's no secret that having a baby affects a couple's sex life. But it's not only because caring for an infant can be exhausting, said Chelom Leavitt, the lead researcher on the new study.
A first-time mom's worries about her new role may be one of the other factors, said Leavitt, a doctoral student in human development and family studies at Penn State University.
The findings are based on interviews with 169 couples who'd recently had their first baby. All were heterosexual and most were married.
When the baby was about 6 months old, the couples were surveyed about parenting stress. They rated how strongly they agreed or disagreed with statements like, "My child smiles much less than I expected," and "I find myself giving up more of my life to meet my child's need than I ever expected."
Later, when their baby was about 1 year old, couples rated their satisfaction with their sex lives.
On average, the researchers found, couples were only "somewhat satisfied." But there was a wide range in responses -- and satisfaction tended to be lower when women had high levels of parenting stress.
It's not clear, though, that stress over parenting is to blame, according to Lonnie Barbach, a clinical psychologist on faculty at the University of California, San Francisco.
Many factors can influence a new mother's sexual satisfaction -- from fatigue and physical discomfort to breast-feeding and body image issues, said Barbach, who wasn't involved in the study.
Leavitt agreed that the study didn't look at whether, for instance, stressed-out moms were more likely to have problems with body image, too. And the researchers didn't gauge couples' sexual satisfaction before the baby arrived -- so it's not clear whether their sex lives actually declined.
Still, Barbach said it's likely that stress over parenting can affect some couples' intimacy.
But why would only moms' parenting stress matter? Leavitt said it may be because men and women have different views on their roles as parents.
Society puts more pressure on new mothers to naturally be "good" at it, whereas new fathers are almost expected to make mistakes.
"In general," Leavitt said, "women are more likely to see motherhood as part of their identity as a woman." And that, she added, could take a toll on some women's sexual satisfaction.
Despite that, women in the study were actually more satisfied with their sex lives, overall, than men were. About 69 percent of mothers were at least somewhat satisfied, versus 55 percent of men.
According to Leavitt, that might be related to expectations. Couples were surveyed when their babies were 12 months old, and at that point many women might have been happy that their sex lives were getting back on track, Leavitt said.
Men, on the other hand, may still have been wanting more.
Barbach agreed. And it's not only because men typically have a greater sex drive, she noted.
"For men, sex is a major way to connect emotionally," Barbach said.
She suggested that if couples are unhappy with their post-baby romantic life, they talk about it -- in a "positive," rather than judgmental, way.
"Talk about how you can make more time for each other," Barbach said. "Have 'date nights.' It's cliche, but it's really important."
She stressed the importance of not "pushing" the sex issue, however -- especially in the first three to six months after the baby is born.
"There's a period where sex just gets put on the back burner," Barbach said.
To Leavitt, the study findings suggest that new parents -- especially moms -- will fare better if they have "realistic expectations."
"Be less judgmental of yourself, and try to enjoy the experiences of being a parent as they come," she said.
The study was published online in the journal Sex Roles.
The March of Dimes has suggestions for coping with 'new mom' stress.
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