New moms know the drill. Wake up for middle-of-the-night feeding. Steal a couple of hours of sleep. Repeat. Even though many new mothers get enough hours of sleep in total, researchers at West Virginia University say that the fact that it’s often fragmented is what takes a toll on new mothers, physically and mentally.

The topic is of particular interest to researchers because earlier studies have suggested a connection between sleep fragmentation and postpartum depression.

For the new study, Hawley E. Montgomery-Downs and colleagues followed 74 new mothers between the second and 16th postpartum weeks. They asked the mothers to keep sleep diaries and to wear an electronic gadget on their wrists, which tracked their movements during the day and night.

On average, the new mothers got over seven hours of sleep per night, which is about the norm for most people. However, their sleep was fragmented to the point that the mothers were awake for an average of two full hours throughout the night. The situation did tend to improve as time wore on: the mothers spent fewer periods awake during the night, so the seven hours of sleep became more condensed as time passed. The researchers underline the fact that the results show that the participants’ sleep became less fragmented and more cohesive as time passed.

The topic is of particular interest to researchers because earlier studies have suggested a connection between sleep fragmentation and postpartum depression. People who suffer from sleep fragmentation, including not only new parents but also people with sleep apnea and periodic limb movement disorder, may have problems aside from feeling tired an unrested during the day. These can include declines in cognitive and overall brain function as well as reduced quality of life. Even partial sleep deprivation can lead to significant cognitive and mood problems.

Montgomery-Downs writes that it may be time for the country to reconsider the current conventions regarding maternity leave from work (which differs significantly from many other countries). "Considering the known impact of sleep disturbance on performance, requiring women to work outside the home and further curtailing their time for sleep may not be in the best interest of the woman, her family, or society." Hopefully more studies looking into the connections between postpartum sleep fragmentation, depression, and overall function will spur a positive change in public policy.

The study was published in the August 17, 2010 online issue of the American Journal of Obstetrics & Gynecology.