(The New York Times News Service) -- Many new mothers may underestimate the toll giving birth and caring for a baby can take on their health, new research shows.

At five weeks postpartum, a majority of new moms were fatigued, had breast discomfort and a decreased desire for sex, the study found.

"This study highlights the need for ongoing rest and recovery beyond four to six weeks postpartum, and the need for more support for women," says study author Pat McGovern, an associate professor in the division of environmental health sciences at the School of Public Health at the University of Minnesota.

"Moms who have just delivered have a great need for support. In other parts of the world, help for new moms and maternity leave is more generous than in this country," says Dr. Nicholas Klein, director of obstetrics and gynecology at Nyack Hospital in Nyack, N.Y.

Under the federal Family Medical Leave Act, women who work for companies with more than 50 employees can take 12 weeks of unpaid medical leave for the birth of a child, explains McGovern.

However, she points out that many women can't afford to take unpaid leave, and the law only covers employees of relatively large companies. That means a lot of women may end up going back to work sooner than they'd like.

According to the study, 76 percent of working mothers return to work within a year after the birth of their child. Forty-one percent of working mothers are back within three months, and nearly one in six is back within the first month after delivery.

McGovern and her colleagues suspected that many of these women were still experiencing delivery-related symptoms or symptoms associated with the demands of caring for a newborn. To see if this was the case, they interviewed more than 700 women five weeks after they had given birth. Most of the women were white and married.

About half had a college education. The average age was nearly 30.

Not surprisingly, about two out of three women reported feeling fatigued. Sixty percent said they had breast discomfort, and 52 percent said they had a decreased interest in sex. Fifty percent of the women said they had sore or irritated nipples, and almost as many women said they were experiencing headaches. Forty-three percent said they had back or neck pain.

Women who delivered by Caesarean section and women who were breast-feeding reported more postpartum symptoms.

McGovern says it wasn't surprising that women who'd had C-sections had more postpartum difficulties, but she was somewhat surprised that women who were breast-feeding had more symptoms, even when the researchers factored out problems specifically associated with breast-feeding, such as sore nipples.

"Breast-feeding babies digest food more rapidly and need to feed more frequently. That's tiring for mom," says McGovern.

McGovern says there's no one "ideal" time for women to head back to work, though she says most women who can afford to take 12 weeks will do so.

"It's really individual to each woman because it's a constellation of so many factors, such as what's the health of the baby and the mother? How much help does she have at home? Is she married or single? What's the nature of her work? Does she like it or hate it? And, is the job flexible?" she says.

McGovern says there needs to be more education for expectant mothers so they know what to anticipate in the postpartum period.

She also says workplaces should be more flexible.

"The postpartum period for the woman and for her family can be rough," says Klein. "The woman needs all the help and support she can get."

Copyright 2006 The New York Times News Service. All rights reserved.