California ? As if new mothers don’t have enough challenges.

Now they need to get adequate sleep if they want to keep postpartum weight off, according to research released Monday from Kaiser Permanente and Harvard Medical School.

New moms who reported getting less than five hours or less of slumber per day when their infants were 6 months old were three times time more likely to carry an extra 11 pounds by the baby’s first birthday, according to a study of 940 women published in this month’s issue of the American Journal of Epidemiology.

The findings, however, aren’t intended to throw up another daunting goal for new mothers, said Erica Gunderson, Ph.D., a Kaiser researcher and lead author of the study.

Rather, women frustrated with their inability to shed pounds packed on during pregnancy now have another strategy besides joining a gym or cutting calories to lose that unwanted excess.

“We should help women get enough sleep, and not just focus on diet and exercise,” said Gunderson.