Swaddling Plus Stomach, Side Sleeping Tied to Risk for SIDS

Karen Blum

May 09, 2016

The risk for sudden infant death syndrome (SIDS) may increase when babies are swaddled and sleep on their stomachs or on their sides, according to a new meta-analysis published online May 9 in Pediatrics.

"The significant risk of SIDS from placing infants on their side or prone to sleep doubled when infants were swaddled, and the SIDS risk associated with swaddling increased with age," write Anna S. Pease, MSc, from the University of Bristol in the United Kingdom, and colleagues.

Being swaddled and placed prone conferred the greatest risk for SIDS among four studies reviewed, the authors found. This practice was rare among control subjects, occurring less than 1% of the time, but was more frequent among SIDS cases (8%). For both the prone and side sleep positions, the risk for SIDS doubled when the infant also was swaddled. There was also a small but significant risk associated with SIDS in infants who were swaddled and placed for sleep on their backs.

The researchers reviewed the literature to try to determine whether swaddling is associated with an increased risk for SIDS. They identified four studies conducted between 1988 and 2006 in three geographical areas including regions of England, Tasmania in Australia, and Chicago, Illinois. The prevalence of swaddling varied in the studies, being "highest in the study from Tasmania in the late 1980s (35.7%) and much lower in Chicago in the mid-1990s (9.2%) and England (10.3%), with a slight decrease in England 10 years later (5.7%)," the authors write.

Investigators compared 760 SIDS cases with 1759 control subjects. The pooled odds ratio (OR) for swaddling in all studies was 1.53 (95% confidence interval [CI], 1.18 - 1.97; P = .001); however, the prevalence of swaddling between studies was variable. To adjust for this, they applied a random effects model, yielding a pooled OR of borderline significance (1.58; 95% CI, 0.97 - 2.58; P = .06).

Swaddled infants tended to be younger (median age, 57 days) compared with nonswaddled infants (median age, 96 days) in all four studies, although there was no significant difference (P = .23) between the age of the swaddled SIDS cases (median age, 55 days) and swaddled control infants (median age, 61 days). Swaddling in all groups peaked at approximately 2 months of age and dropped off steeply between 4 and 6 months of age.

Although the number of infants studied was small, the risk for SIDS from swaddling increased with age, with the highest risk associated with infants aged 6 or more months, who could roll over (OR, 2.53; 95% CI, 1.21 - 5.23).

Across the studies, 17.5% of infants with SIDS were swaddled during their last sleep compared with 10.8% of similar-aged surviving control infants during a designated reference sleep. In all four studies, the proportion of infants swaddled was higher in the SIDS cases than in the control cases; however, only in the UK studies was the association significant, and only in the more recent of these studies did this significance remain after adjusting for other factors.

The work had some limitations, including substantial heterogeneity among the studies resulting from differing swaddling practices across countries and times. In addition, none of the studies adequately described the swaddling technique, and factors associated with SIDS, such as whether the infant shared a bed with the parents, were not adjusted for.

Despite these limitations, the authors write, "these analyses indicate that the current advice to avoid placing infants on their front or side to sleep may especially apply to infants who are swaddled." Health professionals and current guidelines should consider an appropriate age limit at which swaddling should be discouraged, they said.

The review was conducted on behalf of the Epidemiology Working Group of the International Society for the Study and Prevention of Perinatal and Infant Death. The authors have disclosed no relevant financial relationships.

Pediatrics. Published online May 9, 2016. Abstract

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