Introduction

Postpartum depression is the most common complication of childbirth, impacting approximately 19 % of postpartum mothers globally (Fish-Williamson and Hahn-Holbrook, 2023). Postpartum depression is a major public health problem because it raises the risk of parental suicide (Miranda and Patel, 2005; Oates, 2003) and can impair parenting behavior, adversely impacting the cognitive and behavioral development of children (Field, 2010; Paulson et al., 2006). Given the widespread adverse consequences of postpartum depression, significant resources have been devoted to identifying interventions that may help to prevent postpartum depression (Dennis and Dowswell, 2013; Werner et al., 2015). One previously identified target of prevention is parent-infant skin-to-skin contact directly after birth, which has been found to reduce postpartum depression symptoms in parents of preterm or low birthweight infants (Scime et al., 2019). However, no research has examined the effect of infant carrying on postpartum depression symptomatology in healthy parent-infant dyads.
Parent-infant skin-to-skin contact with preterm and low birthweight neonates is a well-established intervention that can improve parental mood by reducing stress (Tessier et al., 1998), enhancing anxiety regulation (Cong et al., 2021), and reducing postpartum depression symptomatology (Feldman et al., 2010). Physiologically, skin-to-skin contact can trigger the release of the bonding hormone oxytocin (Carter et al., 2007; Cong et al., 2015; Mörelius et al., 2015), and decreased levels of the stress hormone cortisol (Takahashi et al., 2011), both of which have been implicated in reduced postpartum depression risk (Yim et al., 2015). Behaviorally, skin-to-skin contact between parents and infants reduces infant crying (Erlandsson et al., 2007), supports breastfeeding (Moore and Anderson, 2007), and bolsters parent-infant bonding (Tessier et al., 1998), all of which may reduce postpartum depression risk (Alimi et al., 2022; Hahn-Holbrook et al., 2017; Shovers et al., 2021). Although less is known about how parent-infant physical contact outside of clinical skin-to-skin interventions may prevent postpartum depression symptomatology, recent studies have shown that infant carrying – by attaching the infant to the caregiver's body with a textile wrap or semi-structured carrier, also known as “babywearing” – shapes some of the same outcomes as direct skin-to-skin contact.
A recent review (Grisham et al., 2023) highlighted a small but growing body of work connecting infant carrying with postpartum mental health and related outcomes. For example, a correlational study found that mothers who self-reported using an infant carrier more often reported less repetitive negative thinking and more positive mental health while infant carrying (Schoppmann et al., 2023). Although no randomized controlled trials have assessed how infant carrying shapes postpartum mental health specifically, a handful of randomized controlled trials showed an effect of infant carrying on potentially related postpartum outcomes, including secure attachment (Anisfeld et al., 1990; Williams and Turner, 2020a) and parental responsiveness during the still-face task (Williams, 2020). Similarly, from data collected as part of the current randomized controlled trial, our group showed that mothers randomly assigned to receive an ergonomic infant carrier in pregnancy were significantly more likely to be breastfeeding at six months compared to mothers in the waitlist control condition (Little et al., 2021). Though this literature is still fairly sparse, the emerging body of work results suggest that infant carrying could have psychological and physiological benefits related to postpartum mental health. Thus far, this hypothesis has not been directly tested.
We examined whether a randomized controlled intervention with infant carriers would result in decreased postpartum depression symptomatology in the first six weeks after birth. We predicted that the infant carrying intervention would reduce postpartum depression symptomatology at 6-weeks postpartum compared to a waitlist control condition. We also predicted an inverse dose-response relationship between infant carrier use and postpartum depression, with more hours of carrier use being associated with fewer postpartum depression symptoms.