Why new mothers feel exhausted despite getting sleep

Motherhood begins with joy, responsibility, and unexpected exhaustion. For many new mothers, the early days with a newborn blur into sleepless nights and foggy mornings. While friends and family may offer advice like “nap when the baby naps,” this simple sleep guidance doesn’t always work.

A new study being presented at SLEEP 2025 has revealed something deeper. The exhaustion many new moms feel isn’t just due to lack of sleep – it’s rooted in the loss of uninterrupted sleep.

Researchers tracked real-world sleep data of first-time mothers using Fitbit devices. What they found shifts our understanding of postpartum fatigue entirely. Even when mothers manage to get enough total sleep hours, the frequent disruptions keep their bodies from truly resting.

As the data shows, these disruptions are not short-lived. They persist well into the following weeks and months, reshaping what maternal recovery really means.

Sleep habits of first time mothers

The study followed 41 first-time mothers between the ages of 26 and 43. They shared their personal wearable sleep data across a span that began a full year before childbirth and extended into their child’s first birthday.

The research team used 5-minute bins to analyze the sleep and wake patterns, and required at least 10 consecutive minutes of sleep or wakefulness to define the start and end of a sleep session.

One key metric they focused on was the “Longest Stretch of Sleep” (LSS). Typically used to track infant sleep, this measure proved incredibly revealing when applied to mothers.

By identifying how long mothers were able to sleep without being woken up, the study captured the true depth of sleep fragmentation. What emerged was a clear picture of profound sleep disruption, even after the first weeks of new motherhood.

Sleep crashes in week one after childbirth

During the first week after childbirth, mothers averaged just 4.4 hours of sleep per day. This is a stark drop from their pre-pregnancy average of 7.8 hours.

But even more concerning was their LSS, which fell from 5.6 hours before pregnancy to just 2.2 hours. Nearly one-third of these new mothers (31.7%) went more than 24 hours without sleep during that first week.

In many ways, this kind of sleep loss is expected during the first few days. However, the story doesn’t end there. While total sleep duration improved gradually over time, the structure of sleep remained fractured. And that proved to be the real problem.

Sleep improves slowly but stays broken

Sleep rose to 6.7 hours in weeks two to seven, then 7.3 hours by week thirteen. But uninterrupted sleep stayed low – just 3.2 to 4.1 hours, far below the 5.5 to 5.6 hours seen pre-pregnancy.

All differences were statistically significant (F > 29.8, P < 0.001), showing that disrupted sleep reflects a lasting biological change, not just a new routine.

Interrupted sleep leaves mothers exhausted

The study was led by Teresa Lillis, a clinical psychologist and adjunct professor in the department of psychiatry and behavioral sciences at Rush University Medical Center in Chicago.

“The significant loss of uninterrupted sleep in the postpartum period was the most dramatic finding,” said Lillis. “While mothers generally returned to their pre-pregnancy total nightly sleep duration after the first postpartum week, the structure of their sleep remained profoundly altered.”

“These results fundamentally transform our understanding of postpartum sleep; it’s not the lack of sleep, but rather, the lack of uninterrupted sleep that is the largest challenge for new mothers.”

This insight challenges old advice and explains why many still feel exhausted despite doing everything “right.”

New sleep patterns, new health risks

Lillis and her team argue that this kind of sleep discontinuity may be a major risk factor for postpartum depression and other related health issues. The quality of sleep, not just the quantity, influences both mental and physical recovery after childbirth.

Their study gives weight to what many new mothers have said for years: “I’m sleeping, but I’m still tired.” Now there’s scientific proof to back up that experience.

Intermittent sleep does not allow the body to complete essential rest cycles, meaning physical repair and mental restoration stay incomplete night after night.

How to help new mothers sleep

“Our results validate the lived experience of new mothers’ exhaustion and provide a new target for sleep-related interventions,” said Lillis. “Rather than simply encouraging mothers to ‘nap when the baby naps’, our findings show that mothers would most benefit from strategies that protect opportunities for uninterrupted sleep.”

This statement signals a shift in how caregivers, partners, and healthcare professionals might support mothers. Helping new moms catch up on lost hours isn’t enough.

What they need are longer blocks of continuous rest – a goal that may require more structural support, such as shared night care, postpartum doulas, or better parental leave options.

What mothers really need after childbirth

This study opens the door for future research into postpartum recovery and maternal mental health. It may also influence policy decisions related to maternity care.

The study was conducted at Washington State University’s Sleep and Performance Research Center.

What’s clear is that uninterrupted sleep is not just a luxury for new mothers – it is a need, as vital as food and medicine, and it deserves serious attention.

The research will be presented on Monday, June 9, during SLEEP 2025 in Seattle. This annual meeting is a collaborative event hosted by the American Academy of Sleep Medicine and the Sleep Research Society.

The findings are published in the journal SLEEP.

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