Infants show lower stress when carried by mothers instead of being in a stroller, study finds

A study of infants in the Netherlands found that, after a mock bath, infants’ stress levels decreased more quickly when their mothers carried them in a chest carrier compared to when they were placed in a pram. This effect occurred regardless of whether the mothers were walking in nature or staying indoors. In contrast, mothers experienced lower stress levels when they remained indoors. The research was published in the Journal of Environmental Psychology.

Infants depend heavily on their caregivers to regulate their responses to stress. When distressed or uncomfortable, they communicate their needs through crying, facial expressions, and body movements. Responsive caregivers interpret these cues and offer comfort through actions like holding, rocking, or feeding.

Physical closeness—such as being held or carried—helps lower an infant’s heart rate and cortisol levels. Touch, warmth, and soothing voices from caregivers activate calming systems in the infant’s brain. This process, known as “co-regulation,” occurs when the caregiver’s presence and actions help stabilize the infant’s physiological and emotional state.

Through repeated experiences of sensitive caregiving, infants begin to learn how to manage their emotions. These interactions foster trust and support the development of secure attachment. Over time, infants internalize these soothing experiences and gradually become better at regulating themselves.

Study author Nicole Rheinheimer and her colleagues aimed to explore whether a 30-minute outdoor walk would help infants regulate stress after a mild laboratory stressor, compared to staying indoors. They also examined whether being carried in a chest carrier, as opposed to riding in a pram, made a difference. In addition, they investigated whether walking through nature had distinct effects compared to remaining indoors.

Free daily newsletter

The study involved 101 mother-infant pairs recruited via social media and flyers. Mothers received a 25-euro voucher for participating and a book for their infant. The researchers divided participants into four groups. All groups were instructed to give their infant a “mock bath”—undressing the infant, “washing” them with a dry cloth, weighing them, and dressing them again—for 12 minutes. This procedure was intended to serve as a mild stressor.

Afterward, two groups went for a 30-minute walk through a green city forest. One group carried their infants in chest carriers (group 1), while the other used prams (group 2). The remaining two groups stayed indoors. One group carried their infants (group 3), and the other used prams (group 4).

During the experiment, the researchers collected saliva samples from mothers and infants at several time points to measure cortisol levels—a marker of stress. Mothers also completed mood assessments after the mock bath and again after the walk or indoor rest period. The researchers recorded how long the infants slept during the study as well.

The results showed that infants carried in chest carriers experienced a greater decrease in cortisol levels than those placed in prams, regardless of whether their mothers walked outdoors or stayed indoors. Infants whose mothers carried them while walking outdoors also slept longer than those who stayed indoors in a pram.

Mothers who carried their infants also experienced greater decreases in cortisol compared to those who used prams. However, mothers who remained indoors showed a larger reduction in cortisol levels than those who went for a walk.

“The current study points towards the potential benefits of outdoor walking in a natural green environment and infant carrying for infants’ stress levels and sleep as well as for mothers’ stress levels and vigor. In light of these positive effects, the findings may inspire future research on time spent outdoors during infancy,” the study authors concluded.

The study contributes to the scientific understanding of the physiological aspects of mother-infant interactions. However, study authors note that the infants did not show an increase in cortisol levels after the “mock bath”, indicating that this procedure did not cause stress, but also that the observed decreases did not represent a recovery from that stressor.

The paper, “Effects of outdoor walking and infant carrying on behavioral and adrenocortical outcomes in mothers and infants,” was authored by Nicole Rheinheimer, Stefania V. Vacaru, Simone Kühn, and Carolina de Weert.