Why Sleeping Close to Your Baby Matters

Source: Dobromir Dobrev / Pexels

One of the most basic ways parents make decisions for their babies is by choosing where they sleep. Co-sleeping—where an infant shares a sleeping surface or room with a parent—has been practiced for thousands of years across cultures. In contrast, solitary sleeping, where infants are placed in a separate room, has become the norm in many Western societies. But what does science say about these sleeping arrangements?

While an enormous amount of research has shown infants’ immature physiology requires close proximity from the mother to regulate all their biological systems, less is known about the effects of sleeping arrangements on infants’ physiology.

In this blog, I will share two studies that are in congruence with the body of research that shows that maternal proximity such as skin-to-skin contact or carrying, is coregulatory for babies.

The first study is by Raghunath et al. (1), who explored how different sleeping arrangements impact infants' physiological state. The researchers measured physiological indicators of the state of the autonomic nervous system, such as heart rate variability (HRV) and Interbeat Interval (IBI), in infants who were napping in three conditions: co-sleeping, sleeping beyond arm’s length, or sleeping alone. Infants were between 1- and 3 months old.

The findings revealed that infants who regularly co-slept with their mothers exhibited the highest levels of physiological calming across all sleep conditions, indicated by longer IBIs. Infants who slept beyond arm’s length had intermediate IBI values, while solitary sleepers had the shortest IBIs, suggesting greater physiological stress due to mother-infant separation.

In addition, co-sleepers had a significantly higher HRV (an indication of a less stressed system) than solitary sleepers across all sleeping conditions. The researchers suggested that co-sleepers are so well regulated that they did not respond to a change in sleeping conditions with a stress response.

The second study by Morgan et al. (2) took an even closer look at the effects of maternal-neonate separation (MNS) on newborns. Their study measured heart rate variability in newborns while sleeping in skin-to-skin contact with their mothers or in a bassinet next to the mother’s bed.

The results were striking: neonates separated from their mothers experienced a 176% increase in autonomic nervous system activity—a sign of stress—and an 86% decrease in quiet sleep, the most restorative type of sleep.

Why Proximity Matters

Why does maternal proximity seem to matter so much? Infants are not evolutionarily designed to sleep alone. Throughout human history, co-sleeping has been the norm, allowing infants to remain in close contact with their mothers for regulation, warmth, and protection. Research shows that skin-to-skin contact regulates an infant's body temperature, reduces cortisol levels (a stress hormone), and improves sleep patterns (3). In contrast, solitary sleeping may disrupt these natural regulatory mechanisms, leading to stress and less effective future self-regulation.

The studies by Raghunath et al. and Morgan et al. suggest that solitary sleep, a practice rooted in modern ideas of independence, may not be ideal for young infants who still rely heavily on external support to regulate their bodies and emotions.

The findings from these two studies have important implications for how we think about infant sleep and parenting. While solitary sleep might seem to foster independence, it’s important to consider the developmental needs of infants during their first years of life. Infants and their physiology require the close presence of a caregiver, and this includes during sleep. It is close proximity in the early years that will later develop independence.

Rather than focusing on “teaching” babies to sleep alone, we should prioritize practices that reduce stress, promote bonding, and support optimal physiological development during this critical period.

While each family’s sleeping arrangements will vary based on cultural, personal, and safety considerations, it’s clear that infants benefit from the comforting presence of their caregivers. Providing proximity to a caregiver -including during sleep- can promote better developmental outcomes and reduce stress in babies—something that may benefit them not just in infancy, but throughout their lives.