Positioning and SIDS

Positioning

and

SIDS

AAP Task Force on Infant Positioning and SIDS

SUMMARY STATEMENT

Based on careful evaluation of existing data

mdi-cating an association between Sudden Infant Death

Syndrome (SIDS) and prone sleeping position for

infants, the Academy recommends that healthy

in-fants, when being put down for sleep, be positioned

on their side or back. The most common position

currently used in the United States is prone.

This recommendation is made with the full

recog-nition that the existing studies have methodologic

limitations and were conducted in countries with

infant care practices and other SIDS risk factors that differ from those in the United States (eg, maternal smoking, types of bedding, central heating, etc).

How-ever, taken as a group the studies are convincing. No

reports show an advantage to the prone position with

regard to SIDS incidence and there are no data prov-ing, or even strongly suggesting, that sleeping in the lateral or supine position is harmful to healthy infants. Thus, assessment of the risk/benefit balance for prone

vs nonprone positioning for such infants favors the

latter. It should be stressed that, the actual risk of SIDS for an infant placed prone is still extremely low.

There are still good reasons for placing certain

infants prone. For premature infants with respiratory distress, for infants with symptoms of gastroesopha-geal reflux or with certain upper airway anomalies,

and perhaps for some others, prone may well be the

position of choice. A nonprone sleeping position is

recommended for healthy infants only.

REPORT

Health care professionals frequently are asked how

it is best to place an infant down for sleep, prone or supine. With lack of scientific studies clearly showing advantages of one position over another, profession-als have tended to offer advice that seems most logical

and to be guided by general custom. However, there

is a growing body of literature reported from Europe,

Australia, and New Zealand that suggests that the

prone sleeping position may be associated with a

higher incidence of Sudden Infant Death Syndrome

(SIDS). This report will review the evidence and offer a recommendation for sleeping position of the healthy baby during early infancy.

The recommendations in this publication do not indicate an exclusive course of treatment or serve as a standard of medical care. Variations, taking into

account individual circumstances, may be appropriate.

PEDIATRICS (ISSN 0031 4005). Copyright ( 1992 by the American

Acad-emy of Pediatrics.

Common Sleep Positions

The predominant infant sleeping position appears

to vary considerably from country to country. In the

United States, most infants are placed in their beds prone (Hoffman H. National Institute of Child Health

and Human Development: Cooperative

Epidemiolog-ical Study of Sudden Infant Death Syndrome Risk

Factors. Personal communication, 1992). Reasons

often cited for this preference include a perceived decrease in the likelihood of aspiration, less

gastro-esophageal reflux,’3 and improved pulmonary

function46 and sleeping.7 Other reasons previously

cited for favoring the prone position include less head

molding,8 improved psychomotor development,7 less

colic,9 possible prevention of infantile scoliosis,1#{176} and

decreasing upper airway resistance in infants with

specific abnormalities of the airway such as are

as-sociated with the Robin Anomaly.’

In parts of Europe’2”3 and Asia,’4’6 infants have

historically been placed in either the lateral or supine position, although until recently there has been little published justification.

Several studies have shown that babies placed

either supine or prone, during the first few months following birth, will generally remain in that position

throughout sleep, while those placed in a lateral

position frequently turn to the supine position, but

seldom to the prone.17”8

Association Between Sleeping Position and SIDS

A possible relationship of the prone position and

SIDS was suggested as early as the 196Os’ and early

19705.20 Since then, a variety of publications have

supported this relationship. Most studies involved

retrospective interviews of parents after their infant had recently died of SIDS or prospective interviews

of parents with children at high risk of SIDS. We

have categorized the studies according to their adher-ence to six criteria that we found to be essential for

appropriate evaluation and comparison (Table 1), and

further grouped them into three categories of study

design: (1) those examining “usual” sleeping position

(Table 2); (2) those examining how the infant was

TABLE 1. Criteria for Study Acceptance.

1.SIDS appropriately defined

2.Autopsies performed in > 98% cases

3. Adequate description of SIDS ascertainment in the study popu-lation

4. Use of controls

5. Adequate description of process of control selection 6. Inclusion of sufficient data to calculate odds ratio and 95%

confidence limits

SIDS = sudden infant death syndrome.

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“last put down” prior to death (Table 3); and (3) those

asking how the infant was “found” following death

(Table 4).

Wherever possible, we have calculated from the

published data the odds ratio2’ of SIDS occurring if

the infants were prone versus the number of infants

prone in the control group. An odds ratio of greater than 1 .0 describes a positive relationship of prone and SIDS for the particular population studied, while

an odds ratio of less than 1 .0 would describe an

inverse relationship (ie, a protective effect of prone).

The range listed in parentheses denotes the 95%

confidence interval for the odds ratio. If the lower limit of the confidence interval is greater than 1.0,

Seven studies comparing “usual sleeping position” of infants who died of SIDS and controls were judged to satisfy all six of our criteria. Six of the seven studies reported a significant correlation of prone position with SIDS, with odds ratios ranging from 1 .3 to 11.7.

Three studies that examined the infant’s position

when “last put down” fulfilled the criteria; all reported

an association between sleeping prone and SIDS, with

odds ratios from 3.53 to 9.46. The one study that

fulfilled criteria and examined the infant’s position

when “found dead” reported that infants were nearly

1 2 times more likely to be found prone, when

com-pared to the usual sleeping position of controls. Even

among those studies that met criteria, many were

associated with some flaw in study design. (For

ex-ample, the study just mentioned determined “found”

position through parental interviews, but estimated “usual” position via a mail survey.) When considered

together, however, the studies present substantial

evidence of an association of prone position and

SIDS, independent of other variables. In three of

these studies, the odds ratio increased further after

accounting for confounding effects of other

vari-ables.2224 No published report has suggested the

converse-ie, a reduced incidence of SIDS with the

prone position.

Several investigators have called attention to the

apparent relationship of predominant sleeping

posi-tion and SIDS incidence when one country is

com-pared to another. Such comparisons must be viewed

very cautiously because of numerous other

coexist-ing cultural differences and variances in data

collec-tion. For example, the SIDS rates among Asians, for

whom supine position is the norm, appear to be very

1OW’4’2528 however, numerous variables such as

swaddling, lack of central heating, and increased

fre-quency of the infant sleeping in the same bed with

the parents29 are also quite different when compared to most Western countries.

Change in SIDS Associated with Change in Sleeping

Position

During the 1970s, infant sleeping position in the

Netherlands reportedly changed from predominantly

supine to predominantly prone. An abrupt increase

in SIDS was noted soon afterward.’8 In the mid 1980s, after several retrospective analyses had noted a

rela-tionship between SIDS and prone position, the lay

press and a few investigators began to advocate

su-pine or lateral positioning rather than prone in other

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*4-countries.3#{176} Subsequently, very preliminary reports

from New Zealand3”32 and the United Kingdom33

noted decreases in the incidence of SIDS by more

than 50%, coincident with a change in sleeping

po-sition from mostly prone to predominantly supine or

lateral. It is quite possible that other variables were also changing during this time.

Hypotheses Regarding Possible Mechanisms

Several hypotheses relating prone position and

SIDS have been proposed, although they certainly

have not been proven. Oropharyngeal obstruction has

been demonstrated to precipitate apnea in preterm

infants3436 and perhaps in some infants through the

first several months after birth.37 Posterior

displace-ment of the mandible with resultant obstruction of

the narrow, relatively vulnerable, pharyngeal airway

of the infant38 may be precipitated by facial

pres-sure,39 which is more likely to occur in the prone

position. Obstruction may also be precipitated by

distortion of the compliant nasal cartilage of the

young infant when prone.4#{176}

An animal model has been developed to explain

how rebreathing, from a pocket formed in the infant’s

bedding which would be more likely to occur in the

prone position, may be responsible for a few cases

of 51D5.4’ Soft or porous sleeping surfaces may

in-crease the likelihood of rebreathing. A proposal

im-plicating a compromise of cerebral blood flow during cervical hyperextension (more likely to occur in prone infants) has been supported by studies with autopsy subjects.4’ Both the airway obstruction and the blood

flow compromise theories have been challenged by

physiologic monitoring studies, involving small

num-bers of subjects during relatively brief time

pe-riods.43’44 Overheating, which may be more likely in

prone infants for whom heat dissipation may be less

effective, has been proposed by several investigators

as a possible mechanism.45’46 Overheating has also

been suggested as a possible explanation for some

intercountry variations, perhaps reflecting differences in climate, heating conditions, and infant dressing customs.47’

Possible Deleterious Effects of Lateral or Supine

Position

If one is to advocate changing the norm, which is

the prone position in the United States, there must be relative assurance that the alternative lateral or supine position is not more hazardous for some other reason,

perhaps unrelated to SIDS. Scoring systems have

been developed for separating healthy infants into

groups that are at high risk or low risk for S1D55254; studies that have examined the effect of position have either not considered risk status or have considered only the high-risk population. Healthy infants at high

risk for SIDS stand to benefit most from avoiding the

prone position. There is a theoretical possibility that infants at low risk for SIDS may have a more adverse risk/benefit ratio. Future observations of infants with

specific risk status may allow an identification of

infants most likely to benefit from one position vs

another.

Despite common beliefs, we discovered no

evi-dence that aspiration is a more frequent complication

in healthy infants lying supine when compared to

other positions. Although we could find no controlled

studies, aspiration is a very rare cause of infant

death.48 One review of infant deaths that were not

related to SIDS reports that the three infants who had aspirated prior to death had all been found prone.47

There are several studies that suggest that

symp-tomatic infants who have documented

gastroesoph-ageal reflux may reflux less in the prone position.’3

Gastroesophageal reflux is common in healthy

in-fants, but only a very small number are symptomatic and develop complications such as esophagitis,

recur-rent pneumonia, failure to thrive, or apparent

life-threatening events. The proposed change in position

is intended for healthy asymptomatic infants only.

Several investigations have demonstrated that

healthy infants4 and preterm infants with respiratory

distress5 have improved oxygenation and pulmonary

function in the prone position, particularly if a depres-sion has been cut in the mattress to facilitate abdom-inal excursions.6

All of these observations may provide good ration-ale for placing some infants prone, as indicated under

“Summary and Recommendations. “ However, no

convincing long-term beneficial effects or positive

influences on decreasing mortality have ever been

shown for the prone position in the populations stud-ied.

Recent Recommendations Regarding Sleep Position in

Other Countries

At least two countries have undertaken formal

action to encourage parents to avoid placing their

infants prone. The New Zealand Cot Death

Preven-tion Programme began in March 1991; it advocates

the lateral or supine sleeping position, discourages

household and maternal smoking, and encourages

breast-feeding.23 On October 31, 1991, the Chief

Medical Officer for the Department of Health for the

United Kingdom issued a press release advocating

that “babies not (be) placed on their tummies when

they are going to sleep.”56 Campaigns against the

prone position have also been mounted by individuals

or foundations in the Netherlands57 and in

Aus-tralia 58

SUMMARY AND RECOMMENDATIONS

Although prospective randomized clinical trials

have not been performed, the weight of evidence

implicates the prone position as a significant risk

factor for SIDS. There is some concern that many of

the studies have come from countries and regions

with SIDS rates which are significantly higher than

that of the United States. Nevertheless, the consist-ency of the results from a variety of countries makes

it more likely that the data should be applicable to

this country as well. In addition for the healthy infant,

there appears to be little hazard associated with the

lateral or supine positions. The preponderance of data have come from studies that asked about “usual” sleep

position, as opposed to position “when found dead”

or “last position seen.” Nevertheless, during the first

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few months after birth, it appears as if the position in which the infant is first placed will substantially determine the position that the infant will maintain

throughout sleep. Therefore, it appears reasonable to

recommend that most healthy infants be placed in

the lateral or supine position.

Many will advocate development of a carefully

controlled clinical trial to test definitively the relation-ship of sleep position and SIDS. In view of the large

population required for a study, the requirement for

lay participation in any trial, and the bias that has

already been introduced by previous publications and

the lay press, it appears unlikely that such an

impar-tial controlled trial could be conducted. However,

there are techniques other than the controlled trial

that can be used to evaluate this issue further. We

encourage ongoing rigorous analysis of the

relation-ship between sleeping position and SIDS in the

United States. Subsequent increases or decreases of

the incidence of SIDS in the United States may reflect

a change in sleeping position or a change in some

other variable. Watching for and reporting possible

changes in selected regions during the next decade

must be a high research priority for investigators and funding agencies.

Although not the subject of this review, it is

im-portant that society recognize that other potentially alterable factors have also been shown to be

associ-ated with SIDS. Maternal smoking and prematurity

have both been identified as risk factors59; breast-feeding has been associated with a decreased risk.6#{176}

Programs aimed at changing these variables may well

lead to improved rates. Also, we want to emphasize

that there are still good reasons for placing certain infants prone. For premature infants with respiratory distress, infants with symptoms of gastroesophageal reflux, infants with certain craniofacial anomalies or

other evidence of upper airway obstruction, and

per-haps some others, prone may well be the position of

choice. It should be stressed that, although the relative

risk of the prone position may be several times that

of the lateral or supine position, the actual risk of

SIDS when placing an infant in a prone position is

still extremely low.

In conclusion, after evaluation of all available

evi-dence to date, for the well infant who was born at

term and has no medical complications, the Academy

recommends that these infants be placed down for

sleep on either their side or back.

AAP TtsK FORCE ON INFANT Posmorsxmic rsm SIDS

John Kattwinkel, MD, Chair University of Virginia

Charlottesville, VA John Brooks, MD University of Rochester Rochester, NY

David Myerberg, MD

West Virginia University

Morgantown, WV

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