Elizabeth Call, a therapist with two small children, was lying in bed with her husband one recent morning. Playing nearby, her four-year-old son found her diaphragm case, which he thought contained vitamins.

While the birth of a child is typically one of the most joyous experiences in a couple’s lifetime, it’s also one of the most challenging times in a marriage.

A study by psychologist John Gottman published in 2000 in the Journal of Family Psychology found that two-thirds of couples experience a significant decline in marriage satisfaction—including less-frequent or less-satisfying sex, more conflict and more emotional distance—after the first baby arrives. The study, funded by the National Institute of Mental Health in the US, involved in-depth interviews with 130 newly-wed couples, 49 of whom became pregnant, and it confirmed similar research findings about marital happiness after children are born.

In Seattle, at his Relationship Research Institute, Dr Gottman oversees an ongoing study called the Bringing Baby Home Project, that has been examining the toll babies can take on a marriage, and is working to develop a hospital-based counselling programme to help prepare new parents for what can be a chaotic time. Last year, a major report from the National Marriage Project at Rutgers University, noted that many Americans now view life before children, and after they fly the coop, as the most satisfying years of adulthood, while children are viewed more as a disruptive force and an obstacle to marital happiness.

There are many reasons for discord when a baby comes home. Sleep deprivation, loss of freedom, lack of time and keeping score on who does more dishes explain some of it. But now marriage researchers are beginning to take a closer look at a less-talked-about casualty of parenting: a couple’s sex life.

The fact that many new parents often feel like strangling each other instead of smooching is fuelling a “boomlet" of advice books, including And Baby Makes Three, by Dr Gottman and his wife, Julie Schwartz Gottman, and Babyproofing Your Marriage, written by three mothers and published earlier this year. New York marriage and family therapist Esther Perel’s Mating in Captivity, which tries to help couples reconcile the romantic and the domestic spheres, came out in the fall.

The books argue that new parents who regard sex as something extra in their lives are making a mistake. Restoring your sex life and intimate bonds, they say, will help resolve other issues that arise when babies arrive. The books offer some overlapping advice for new parents: Communication is key, sex—even quickie sex—is critical and date nights are essential. And if you make it until the kids reach four or five, it gets easier—when sleeping patterns, school and childcare arrangements become less fraught.

The popularity of these and other books in the genre underscores the perils of new parenthood, but also suggests there’s a growing desire by parents to try to repair frazzled bonds. “The conventional wisdom seems to be that the birth of a child will usher in this lovely romantic period with your husband, it’s all soft focus and Hallmark moments," says Babyproofing co-author Cathy O'Neill. “But these expectations are way out of whack and many of us end up compulsive and crazy in ways we never imagined."

Peggy Kaufman, a clinical social worker, says it seems more parents are willing to talk openly about the distress they face after the birth of children. While the topic is not new, she says, it seems older parents—who have had many more years to establish their habits and enjoy their freedom—may harbour more resentment about the sacrifices children require. Women, in particular, may expect their partners to take on an equal share of work, and end up shocked when that doesn’t happen. Disappointment is a major complaint, she says.

Indeed, marriage experts note that men and women often have different takes on the problems in their relationships. Women feel unappreciated and bitter that their partners don’t help more with childcare and chores. Men want their wives to re-establish their pre-baby sex appeal. “Men are much more ready to get a babysitter, go to a movie, leave the baby overnight," Kaufman says. After the six-week post-natal check up, “he wants to have sex and she’s, like, I’m giving and giving and giving—I can’t physically give any more."

Beth Soltzberg, 39, says she fantasized about kicking her snoring husband out of bed in the first months after their son was born. They fought often and their sex life dwindled to next to nothing. “I didn’t feel that I had anything to give him, or wanted to give him," says Soltzberg, who left a job in health-care consulting after having children. “He wasn’t acknowledging or appreciating what I was doing."

One solution offered by the experts: Redefine romance. Instead of nuzzling the nape of his wife’s neck, a man may have more romantic success if he makes the dinner or bathes the kids, they say.

The Gottmans say that through their research studying how couples interact, they have come up with a six-point plan for rekindling romance post-kids. Among other things, they say, try to de-escalate conflicts with kinder, more accepting words. Turn toward each other—not away—for friendship and sex. The role of fathers, who may often feel left out or clueless, especially when the baby is an infant, should be emphasized. And couples need to remember that children are their legacy, so they should try to take the long view about the short-term disruption they can cause.

Rutgers University anthropologist Helen Fisher, who studies the brain circuitry of romantic love, says millions of years of evolutionary adaptation account for a couple’s divergent sexual interests after kids are born. For instance, when a woman is nursing and holding her child, levels of the hormone, oxytocin, surge, leading to intense feelings of attachment. Testosterone levels, which are related to sex drive, plummet. “Mom’s not just overly tired and making excuses—she’s drugged," Dr Fisher says. “From a Darwinian, evolutionary perspective, if mom’s not there to take care of the baby, it will get eaten by a lion. Both parents are fighting a basic evolutionary mechanism that evolved to strengthen the mother/infant and parental bond, not the sexual bond."

But men and women can fight the chemical reaction with more brain chemicals, she says. Any kind of sexual stimulation drives up dopamine, which is associated with romantic love, and triggers other “feel good" hormones to wash over the brain. Dr Fisher says this means couples should have sex even if they don’t feel like it.

Dr Fisher advises parents to think about sex like exercise—it’s healthy and even if you may not be up for it initially, it generates good feelings afterward. Dr Fisher notes that positive hormones are released whether the sex lasts for minutes or hours.

Part of the problem is that men and women have different expectations concerning sex. Dr Gottman says that his 13-year study of couples confirms the divide: Men on an average want to have sex four times a week while women want it once a week.

Rich Porter, a 46-year-old father of a two-year-old, says he is more interested than his wife is in their love life. “She’s overtaxed," he says. But he acknowledges the stress his wife is under as a stay-at-home mom, and expects that when the child is older and more independent, things will get better.

Some women say it’s not that they don’t want sex, it’s just difficult to find the perfect moment. Jill Harlan, the mother of a 19-month-old, who runs a non-profit out of her home, says some of her best days, sexually speaking, are when her daughter is at day care, and her husband, a medical resident, has the day off. “Day care," she says, “is the best thing that’s ever happened to me."

And Soltzberg, with the snoring husband, says their relationship survived the “crisis" of having a baby, and is now even stronger for it, aided by marriage counselling, more dates and a strong desire to constantly work on the relationship.

(Write to wsj@livemint.com)