compiled by Rosemary Horne, Melbourne, Australia, spokesperson of the ISPID Physiology Working Group

Swaddling, or firm wrapping, is a traditional infant care practice which has been used in some form or another by various cultures since medieval and ancient times [1]. Low SIDS incidences associated with populations where swaddling is common, have led to proposal that swaddling may be protective for SIDS [2, 3]. However in relation to the risk of SIDS, the role of swaddling has been difficult to determine. In one study, a reduced risk of SIDS was observed when bedding was firmly tucked in (OR = 0.63), however this protective effect may have been a consequence of the reduced probability of head-covering by loose bedding or the inability of infants to roll into the high-risk prone position [4]. In another study, Ponsonby et al. [5] found that swaddling increased the risk of SIDS when infants slept in the prone position (to 12-fold from 3-fold when infants were unswaddled), but had no significant effect on SIDS risk when infants slept supine/lateral. In the United Kingdom during the mid-1990s, swaddling during the last sleep was more common amongst SIDS infants than age-matched controls (14% vs. 9%); furthermore, a more recent study showed that this difference has since become more marked (19% vs. 6%) [6].

Additional concerns raised regarding swaddling have included potentially increased incidences of developmental hip dysplasia, acute respiratory infections and overheating [7-9]; however these complications may be circumvented by modifying the swaddling style used and by avoiding extra bedding.

Numerous studies have documented a "tranquil" behavioural state and longer sleep periods in swaddled infants [10-14]. Thus, despite the unknown effects on the risk for SIDS, swaddling is becoming increasingly popular as a settling technique in the Netherlands, the United Kingdom and the United States [15, 16]. It has been suggested that by effectively pacifying distressed infants, swaddling may reduce parental-child tension. Furthermore, a style of swaddling has been suggested by some Australian SIDS organizations as a method to settle infants in the supine position, with the aim of reducing the prevalence of upset infants being placed prone.

These findings logically suggest that infant swaddling would increase infant sleep time by preventing awakening. However this may not be a desirable outcome, as the pathogenesis of SIDS is thought to involve an impaired ability to arouse from sleep in response to a life threatening respiratory or cardiovascular challenge [17]. Arousal from sleep in infants is a hierarchical response proceeding from sub-cortical activation involving changes in heart rate and breathing, to full cortical arousal involving changes in brain activity; and this progression has been reported to be incomplete in infants who later died of SIDS [18]. Infant swaddling has been shown to minimise arousals from sleep, crying time, spontaneous startles and the progression to full arousal [1, 12, 14, 19]. In contrast, other studies have reported that infants are more sensitive to auditory challenges and arouse more readily in active sleep when swaddled [13, 20]. Recent studies carried out in Australia have examined both arousal responses to external stimuli and spontaneous arousal from sleep in infants who were routinely swaddled at home and those who were not (i.e. were naïve to swaddling) [21, 22]. Infants were studied at both 1 month (when SIDS risk is low) and 3 months of age (the peak age of SIDS risk), both unswaddled and swaddled in light muslin (cotton) wrap with their arms folded across the chest, as recommended by the Australian SIDS and Kids website. The study reported a decrease in total arousability (i.e. increased arousal thresholds to nasal air-jet stimulation) when infants were swaddled, together with a decrease in the frequency and duration of cortical arousals. When the usual care practice of the infants was considered, swaddling had no effect on the arousability of infants who routinely slept swaddled at home, yet a significant decrease in both total arousability and frequency of cortical arousal was observed in the infants who were not accustomed (naïve) to being swaddled. Additionally, in the naïve group only, a decrease in spontaneous cortical arousals was also observed with swaddling [23].

These findings suggest that arousal suppression may not simply be a consequence of swaddling per se, but rather, of being unfamiliar with sleeping swaddled. This concept of risks associated with unfamiliar sleeping conditions might also apply to other care practices; for example, there have been numerous reports of increased SIDS incidence and compromised airway protective behaviours in infants who were inexperienced in sleeping in the prone position [24-26]. Of particular relevance to SIDS, the effects of swaddling on arousal in our study were primarily observed when infants were 3 months old, corresponding not only with the age of peak SIDS incidence, but also with the time that many mothers return to work [27, 28]. Thus, adopting unfamiliar sleep practices at this age may have grave implications for infants being cared for by secondary caregivers, particularly as many do not consider how infants are placed to sleep at home. Highlighting this risk, it has previously been hypothesised that a change in routine care may be associated with the disproportionately high percentage of SIDS deaths (16%) in organised child care programmes [29, 30]. The finding of altered arousability only in the naïve to swaddling group of infants provides new physiological support for this concern.

Recommendations

• Parents should be aware of the potential risks of swaddling their infant, particularly of the use of heavy materials for swaddling.
• Infants must NEVER be placed prone (on their stomach) when swaddled.
• Current research suggests that it is safest to swaddle infants from birth and not to change infant care practices by beginning to swaddle their infant at 3 months of age when SIDS risk is greatest.
• Secondary caregivers should be made aware of their infant's usual sleeping environment and practices.

References

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22. Richardson HL, Walker AM, Horne RSC. Sleeping like a baby – Does gender influence infant arousability? Sleep 2010; in press.
23. Richardson HL, Walker AM, Horne RSC. Influence of swaddling experience on spontaneous arousal patterns and autonomic control in sleeping infants. Journal of Pediatrics 2010; in press.
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• Photograph: Baby-kokon11.jpg (curtailed)
• Photographer: Produnis
• Original picture here

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