Sudden infant death syndrome and sleeping position in pre-term and low birth weight infants: an opportunity for targeted intervention

Aims

To determine the combined effects of sudden infant death syndrome (SIDS) risk factors in the sleeping environment for infants who were “small at birth” (pre‐term (<37 weeks), low birth weight (<2500 g), or both).

Methods

A three year population based, case‐control study in five former health regions in England (population 17.7 million) with 325 cases and 1300 controls. Parental interviews were carried out after each death and reference sleep of age matched controls.

Results

Of the SIDS infants, 26% were “small at birth” compared to 8% of the controls. The most common sleeping position was supine, for both controls (69%) and those SIDS infants (48%) born at term or ⩾2500 g, but for “small at birth” SIDS infants the commonest sleeping position was side (48%). The combined effect of the risk associated with being “small at birth” and factors in the infant sleeping environment remained multiplicative despite controlling for possible confounding in the multivariate model. This effect was more than multiplicative for those infants placed to sleep on their side or who shared the bed with parents who habitually smoked, while for those “small at birth” SIDS who slept in a room separate from the parents, the large combined effect showed evidence of a significant interaction. No excess risk was identified from bed sharing with non‐smoking parents for infants born at term or birth weight ⩾2500 g.

Conclusion

The combined effects of SIDS risk factors in the sleeping environment and being pre‐term or low birth weight generate high risks for these infants. Their longer postnatal stay allows an opportunity to target parents and staff with risk reduction messages.     

Prematurity,sleeping position and sudden infant death syndrome

Preterm birth and prone sleeping position significantly increase the risk of sudden infant death syndrome (SIDS). The reduced incidence of SIDS with supine sleeping has been well publicised, yet some prematurely born infants are slept prone at the high-risk age for SIDS. This may reflect inadequate educational targeting of high-risk groups and/or concerns about possible adverse effects of supine sleeping. In addition, parents may receive mixed messages about sleeping positions, as they witness their prematurely born infants being nursed prone on neonatal units, often for many weeks. In the neonatal period, the prone position improves oxygenation, tidal volume and compliance of preterm infants with respiratory distress. The limited data available suggest prone positioning is also beneficial for convalescent, preterm infants. Thus, it is not clear when the advantages of prone sleeping cease. Studies are required to determine when supine sleeping for prematurely born infants can safely be recommended and hence an unambiguous message given to parents.     

An 8 year study of risk factors for SIDS: bed-sharing versus non-bed-sharing.

BACKGROUND: It is unclear if it is safe for babies to bed share with adults. In Ireland 49% of sudden infant death syndrome (SIDS) cases occur when the infant is bed-sharing with an adult. OBJECTIVE: To evaluate the effect of bed-sharing during the last sleep period on risk factors for SIDS in Irish infants. DESIGN: An 8 year (1994-2001) population based case control study of 287 SIDS cases and 831 controls matched for date, place of birth, and sleep period. Odds ratios and 95% confidence intervals were calculated by conditional logistic regression. RESULTS: The risk associated with bed-sharing was three times greater for infants with low birth weight for gestation (UOR 16.28 v 4.90) and increased fourfold if the combined tog value of clothing and bedding was > or =10 (UOR 9.68 v 2.34). The unadjusted odds ratio for bed-sharing was 13.87 (95% CI 9.58 to 20.09) for infants whose mothers smoked and 2.09 (95% CI 0.98 to 4.39) for non-smokers. Age of death for bed-sharing and sofa-sharing infants (12.8 and 8.3 weeks, respectively) was less than for infants not sharing a sleep surface (21.0 weeks, p<0.001) and fewer bed-sharing cases were found prone (5% v 32%; p = 0.001). CONCLUSION: Risk factors for SIDS vary according to the infant's sleeping environment. The increased risk associated with maternal smoking, high tog value of clothing and bedding, and low z scores of weight for gestation at birth is augmented further by bed-sharing. These factors should be taken into account when considering sleeping arrangements for young infants.     

Risk factors for sudden infant death syndrome following the prevention campaign in New Zealand: a prospective study

OBJECTIVES: To identify the risk factors for sudden infant death syndrome (SIDS) following a national campaign to prevent SIDS. METHODS: For 2 years (October 1, 1991 through September 30, 1993) data were collected by community child health nurses on all infants born in New Zealand at initial contact and at 2 months. RESULTS: There were 232 SIDS cases in the postneonatal age group (2.0/1000 live births) and these were compared with 1200 randomly selected control subjects. Information was available for 127 cases (54.7%) and 922 (76.8%) of controls. The previously identified modifiable risk factors were examined. The prevalence of prone sleeping position of the infant was very low (0.7% at initial contact and 3. 0% at 2 months), but was still associated with an increased risk of SIDS. In addition, the side sleeping position was also found to have an increased risk of SIDS compared with the supine sleeping position (at 2 months: adjusted odds ratio (OR) = 6.57; 95% confidence interval (CI) = 1.71, 25.23). Maternal smoking was found to be the major risk factor for SIDS. Bed sharing was also associated with an increased risk of SIDS. There was an interaction between maternal smoking and bed sharing on the risk of SIDS. Compared with infants not exposed to either bed sharing or maternal smoking, the adjusted OR for infants of mothers who smoked was 5.01 (95% CI = 2.01, 12.46) for bed sharing at the initial contact and 5.02 (95% CI = 1.05, 24. 05) for bed sharing at 2 months. In this study breastfeeding was not associated with a statistically significant reduction in the risk of SIDS. The other risk factors for SIDS identified were: unmarried mother, leaving school at a younger age, young mother, greater number of previous pregnancies, late attendance for antenatal care, smoking in pregnancy, male infant, Maori ethnicity, low birth weight, and shorter gestation. CONCLUSIONS: After adjustment for potential confounders, prone and side sleeping positions, maternal smoking, and the joint exposure to bed sharing and maternal smoking were associated with statistically significant increased risk of SIDS. A change from the side to the supine sleeping position could result in a substantial reduction in SIDS. Maternal smoking is common in New Zealand and with the reduction in the prevalence of prone sleeping position is now the major risk factor in this country. However, smoking behavior has been difficult to change. Bed sharing is also a major factor but appears only to be a risk to infants of mothers who smoke. Addressing bed sharing among mothers who smoke could reduce SIDS by at least one third. Breastfeeding did not appear to offer a statistically significant reduction in SIDS risk after adjustment of potential confounders, but as breastfeeding rates are comparatively good in New Zealand, this result should be interpreted with caution as the power of this study to detect a benefit is small.     

Factors relating to the infant's last sleep environment in sudden infant death syndrome in the Republic of Ireland.

AIM: To identify risk factors for sudden infant death syndrome (SIDS) in the sleeping environment of Irish infants. METHODS: A five year population based case-control study with parental interviews conducted for each case and three controls matched for age, place of birth, and last sleep period. A total of 203 SIDS cases and 622 control infants born 1994-98 were studied. RESULTS: In a multivariate analysis, co-sleeping significantly increased the risk of SIDS both as a usual practice (adjusted OR 4.31; 95% CI 1.07 to 17.37) and during the last sleep period (adjusted OR 16.47; 95% CI 3.73 to 72.75). The associated risk was dependent on maternal smoking (OR 21.84; 95% CI 2.27 to 209.89), and was not significant for infants who were > or =20 weeks of age (OR 2.63; 95% CI 0.49 to 70.10) or placed back in their own cot/bed to sleep (OR 1.07; 95% CI 0.21 to 5.41). The use of pillows, duvets, and bedding with tog value > or =10 were not significant risk factors when adjusted for the effects of confounding variables, including maternal smoking and social disadvantage. However, the prone sleeping position remains a significant SIDS risk factor, and among infants using soothers, the absence of soother use during the last sleep period also significantly increased the SIDS risk (OR 5.83; CI 2.37 to 14.36). CONCLUSION: Co-sleeping should be avoided in infants who are <20 weeks of age, or whose mothers smoked during pregnancy. The prone position remains a factor in some SIDS deaths, and the relation between soother use and SIDS is a complex variable requiring further study.     

Factors relating to the infant's last sleep environment in sudden infant death syndrome in the Republic of Ireland

Aim: To identify risk factors for sudden infant death syndrome (SIDS) in the sleeping environment of Irish infants. Methods: A five year population based case-control study with parental interviews conducted for each case and three controls matched for age, place of birth, and last sleep period. A total of 203 SIDS cases and 622 control infants born 1994–98 were studied. Results: In a multivariate analysis, co-sleeping significantly increased the risk of SIDS both as a usual practice (adjusted OR 4.31; 95% CI 1.07 to 17.37) and during the last sleep period (adjusted OR 16.47; 95% CI 3.73 to 72.75). The associated risk was dependent on maternal smoking (OR 21.84; 95% CI 2.27 to 209.89), and was not significant for infants who were ⩾20 weeks of age (OR 2.63; 95% CI 0.49 to 70.10) or placed back in their own cot/bed to sleep (OR 1.07; 95% CI 0.21 to 5.41). The use of pillows, duvets, and bedding with tog value ⩾10 were not significant risk factors when adjusted for the effects of confounding variables, including maternal smoking and social disadvantage. However, the prone sleeping position remains a significant SIDS risk factor, and among infants using soothers, the absence of soother use during the last sleep period also significantly increased the SIDS risk (OR 5.83; CI 2.37 to 14.36). Conclusion: Co-sleeping should be avoided in infants who are <20 weeks of age, or whose mothers smoked during pregnancy. The prone position remains a factor in some SIDS deaths, and the relation between soother use and SIDS is a complex variable requiring further study.     

Prone sleeping position and SIDS: Evidence from recent case-control and cohort studies in Tasmania

The most recent data from the cohort and case-control studies of SIDS and prone position recently reported from Tasmania are reviewed. The cohort analysis was based on 4103 infants born between 1 January 1988 and 1 December 1990 assessed as being at high risk at birth, of whom 29 later died of SIDS. A matched analysis which controlled for infant birthweight and maternal age indicated that prone sleeping position was associated with an increased risk of SIDS (OR 3.92, 95% Cl [1.37-11.24]). The case-control study was based on all (n = 55) Tasmanian SIDS death from October 1989 to April 1991 and matched live controls. The unadjusted odds ratio for prone position and SIDS was 5.04 (95% Cl [2.29-11.11]). The population attributable risk percentage, based on the high risk cohort data, was 0.38 (95% Cl [0.35-0.41]), suggesting that a significant reduction in SIDS incidence might occur if the prevalence of the prone sleeping position in the infant population were reduced. Other factors which may be important for the development of any public health interventions to reduce SIDS based on these findings are discussed.     

Interactions of infectious symptoms and modifiable risk factors in sudden infant death syndrome. The Nordic Epidemiological SIDS study

The aim of the study was to investigate the effect of infection on sudden infant death syndrome (SIDS) and to analyse whether modifiable risk factors of SIDS, prone sleeping, covered head and smoking act as effect modifiers. In a consecutive multicentre case-control study of SIDS in Denmark, Norway and Sweden, questionnaires on potential risk factors for SIDS were completed by parents of SIDS victims, and for at least two controls matched for gender, age and place of birth. All SIDS cases were verified by an autopsy. The study comprised 244 SIDS cases and 869 controls, analysed by conditional logistic regression. Significantly more cases than controls presenting symptoms of infectious diseases during the last week and/or last day were treated with antibiotics and had been seen by a physician. The finding is consistent with the hypothesis of an infectious mechanism in SIDS induced by local microorganism growth and toxin or cytokine production, and also adds further support to a possible association between infection and SIDS by loss of protective mechanisms, such as arousal. The risk of SIDS among infants with the combined presence of infectious symptoms and either of the other modifiable risk factors, prone sleeping, head covered or parental smoking, was far greater than the sum of each individual factor. These risk factors thus modify the dangerousness of infection in infancy.     

A competing risk model of sudden infant death syndrome incidence in two US birth cohorts

OBJECTIVES: To compare changing incidence and changing risk factors associated with sudden infant death syndrome (SIDS) in the 1989 and 1996 US birth cohorts. STUDY DESIGN: All available singleton births over 500 g from the 1989 linked birth-infant death file and the 1996 and 1997 Perinatal Mortality files were examined. A log-logistic survival model was used to explicitly account for declining competing risks among low birth weight infants. RESULTS: Controlling for maternal prenatal smoking and other confounders, SIDS incidence declined by >33% between the 2 survey years (adjusted odds ratio = 0.628 with 95% CI [0.598, 0.660]). Self-reported declines in maternal prenatal smoking were also associated with significant declines in SIDS incidence. African American infants and infants born weighing <1000 g experienced increased relative risk compared with non-Hispanic white infants born weighing >2500 g. Hispanic/Latino infants had significantly lower SIDS risk than non-Hispanic white infants in both years. Accounting for declining competing risks and other factors, relative SIDS risks among infants born between 500 and 1000 g increased over the study period. CONCLUSIONS: SIDS incidence sharply declined between 1989 and 1996. High incidence of SIDS in African Americans and increased relative SIDS risk for infants born weighing <1000 g require increased attention from clinicians and public health policy makers.     

Why do ALTE infants not die in SIDS?

Aim: To compare known risk factors for sudden infant death syndrome (SIDS) amongst infants with apparent life threatening events (ALTE) with their matched controls, and ALTE infants who subsequently died of SIDS with infants surviving an ALTE.
Methods: Questionnaires with replies were obtained from 58 ALTE infants and 56 sex and age matched ALTE control infants. 244 SIDS cases and 868 SIDS controls were used as comparison.
Results: The incidence of ALTE was found to be 1.9% among SIDS controls, but 7.4% among infants who later on died of SIDS. The parents sought medical advice in 0.9% vs 3.7%. ALTE infants did not differ from their matched controls. In the ALTE group 13.3% of the survivors had the combination of prone sleeping and maternal smoking compared with 33.3% of those who became SIDS victims.
Conclusions: Our results show some major differences between the ALTE infants and SIDS victims not supporting that these conditions belong to the same entity. However, we cannot exclude the possibility that there is a subpopulation of ALTE infants who did not die in SIDS due to that they were sleeping on the back and not exposed to nicotine.     

Relationship of sudden infant death syndrome to maternal smoking during and after pregnancy.

Sudden infant death syndrome (SIDS) is associated with maternal smoking during pregnancy. However, the relationship between tobacco exposure during infancy and SIDS is unknown. The examination of infants whose mothers smoked only after pregnancy will help determine the relationship between passive cigarette exposure during infancy and SIDS risk. This case-control analysis used data on normal birth weight (> or = 2500 g) infants included in the National Maternal and Infant Health Survey, a nationally representative sample of approximately 10,000 births and 6000 infant deaths. Infants were assigned to one of three exposure groups: maternal smoking during both pregnancy and infancy (combined exposure), maternal smoking only during infancy (passive exposure), and no maternal smoking. SIDS death was determined from death certificate coding. Logistic regression was used to adjust for potentially confounding variables. Infants who died of SIDS were more likely to be exposed to maternal cigarette smoke than were surviving infants. Among black infants the odds ratio was 2.4 for passive exposure and 2.9 for combined exposure. Among white infants the odds ratio was 2.2 for passive exposure and 4.1 for combined exposure. After adjustment for demographic risk factors, the odds ratio for SIDS among normal birth weight infants was approximately 2 for passive exposure and 3 for combined exposure for both races. These data suggest that both intrauterine and passive tobacco exposure are associated with an increased risk of SIDS and are further inducement to encourage smoking cessation among pregnant women and families with children.     

Sleeping position and sudden infant death syndrome in Norway 1967-91

OBJECTIVE--To investigate, in a population based national study, the association between sleeping position of infants and the occurrence of sudden infant death syndrome (SIDS). DESIGN--A retrospective survey and registry based ecological study. A questionnaire based surveillance of sleeping position was obtained in a random sample (n = 34,799) and surveillance of SIDS was based on all infants born in Norway 1967-91, surviving the perinatal period. Variables studied from the questionnaire were usual sleeping position (placed), breast feeding at 3 months, and maternal smoking in pregnancy, and from the Medical Birth Registry maternal age, birth order, and birth weight. RESULTS--Proportion of infants sleeping prone increased from 1970 (7.4%) to 1989 (49.1%) and dropped in 1990 (26.8%) and 1991 (28.3%). Occurrence of SIDS increased from 1970 (1.1/1000) to 1989 (2.0) before dropping in 1990 and 1991 (1.1). IMPLICATION AND RELEVANCE OF RESULTS--A cause effect relationship between prone sleeping and SIDS as suggested in previous studies is supported by the present; and so far only, national study of infants' sleeping position.     

Sleeping position and sudden infant death syndrome in Norway 1967-91.

OBJECTIVE--To investigate, in a population based national study, the association between sleeping position of infants and the occurrence of sudden infant death syndrome (SIDS). DESIGN--A retrospective survey and registry based ecological study. A questionnaire based surveillance of sleeping position was obtained in a random sample (n = 34,799) and surveillance of SIDS was based on all infants born in Norway 1967-91, surviving the perinatal period. Variables studied from the questionnaire were usual sleeping position (placed), breast feeding at 3 months, and maternal smoking in pregnancy, and from the Medical Birth Registry maternal age, birth order, and birth weight. RESULTS--Proportion of infants sleeping prone increased from 1970 (7.4%) to 1989 (49.1%) and dropped in 1990 (26.8%) and 1991 (28.3%). Occurrence of SIDS increased from 1970 (1.1/1000) to 1989 (2.0) before dropping in 1990 and 1991 (1.1). IMPLICATION AND RELEVANCE OF RESULTS--A cause effect relationship between prone sleeping and SIDS as suggested in previous studies is supported by the present; and so far only, national study of infants'' sleeping position.     

Physician beliefs and practices regarding SIDS and SIDS risk reduction

The AAP has alerted pediatricians to the importance of safe sleep environment for infants. The elements of a safe sleep environment include supine sleep position, safe crib, and avoidance of smoke exposure, soft bedding, and overheating. With the Back to Sleep campaign, prone sleeping among all U.S. infants has decreased to less than 20%, and the incidence of SIDS has decreased 40%. However, the decline in SIDS and prone sleeping has leveled off in recent years. Further declines may be possible with decreasing other modifiable risk factors, such as prenatal and postnatal exposure to cigarette smoking. Prior studies have demonstrated that health care professional advice is influential in determining infant care practices. It is important that physicians caring for infants be aware of the importance of a safe sleep environment and understand other modifiable risk factors for SIDS. We surveyed a random sample of 3,717 physicians in North Carolina and the metropolitan Washington, DC, area to determine knowledge, beliefs, and practices regarding SIDS and SIDS risk reduction among physicians caring for pregnant women and infants. Twenty-three percent (835) responded. Most physicians are aware of prone sleeping and cigarette smoke exposure as risk factors for SIDS. Almost all physicians agree that there are measures that can be taken to reduce the risk of SIDS, and they consider it important to discuss SIDS and SIDS risk reduction strategies with parents of young infants. In spite of this belief, only 56% of family/general practitioners, 18% of obstetrician-gynecologists, and 79% of pediatricians discuss SIDS routinely. Only 35% of pediatricians, 15% of family/general practitioners, and 16% of obstetrician-gynecologists provide written information. In addition, only 38% of physicians recommend supine, while 50% recommend side or back, 6% side, and 7% prone. Only two thirds of pediatricians and one third of family/general practitioners are aware that the AAP recommends supine as the preferred sleep position for infants. Pediatricians are more likely to be aware of the AAP recommendation (p<0.0001) and to discuss SIDS risk reduction strategies with parents (p=0.03). We conclude that many physicians who care for infants are unaware of the AAP's most current recommendation for sleep position and are incorrectly recommending the side position. Physicians may also be unaware of other sleep environment hazards. Further educational efforts must continue for physicians who provide care to pregnant women and children to ensure a continued decline in the incidence of SIDS.     

Sudden infant death syndrome: How much mothers and health professionals know

Background: Behavioral risk factors are associated with sudden infant death syndrome (SIDS). Education about the risk factors of SIDS is important for prevention. Our aim was to determine the knowledge and attitude of parents and health professionals about SIDS. Methods: A total of 174 health professionals and 150 mothers were enrolled in this study. Mothers' data were collected by telephone interview and health‐care professionals were interviewed by the same investigator. Results: Only 39% of mothers were aware of SIDS. Forty‐six percent of the mothers preferred a supine sleeping position for their infant and 16% of the parents were bed‐sharing with their infants. Seventy‐three percent of health professionals selected side, 17% supine and 10% prone sleeping position as the safest sleeping position. Frequencies for awareness of risk factors were: bed‐sharing (75%), soft bedding (70%), pillow use (52%), toys in bed (90%), high room temperature (67%) and smoking (88%). Total knowledge score of health professionals who selected supine sleeping position as the safest was significantly higher (P < 0.001). Conclusion: Most of the mothers were unaware of SIDS and less than half preferred a supine sleeping position for their infant. Only 72% of health professionals recommended a certain sleeping position during family interviews. Health professionals are more often recommending the side sleeping position or prone. Education of families and health professionals for the risk factors of SIDS may reduce the number of deaths from SIDS in Istanbul.     

SUDDEN INFANT DEATH IN COPENHAGEN 1956–1971

ABSTRACT. 131 cases of the Sudden Infant Death Syndrome (SIDS) among infants born in the Municipality of Copenhagen in 1956-71 were analysed on the basis of data collected prospectively by the infant health visitors. Compared with living controls, the frequency of maturity and the mean birth weight and length were lower among the SIDS infants. After making the SIDS and control groups comparable with respect to birth weight and type of feeding, we found a tendency towards a slower growth rate among the SIDS victims. The SIDS victims started to smile and prattle later than controls, while there was no difference as regards the average age at which the infants became able to hold their heads. It is concluded that the differencses are so small and the individual variations so wide that birth weight and length, growth rate, and psychomotor development will not be useful predictors of the SIDS.     

Is baby too warm? The use of infant clothing,bedding and home heating in Victoria,Australia.

Overheating of infants has been associated with a raised risk for sudden infant death syndrome (SIDS). Data on the use of heating, bedding and clothing and other measures affecting the thermal environment of 4 week old infants were collected at a home interview for infants of women born in Australia (Anglo-Celtic background), in Southern Europe, in Asia and of women who had a planned out-of-hospital birth. These groups have different risks of SIDS not explained by the classic social and perinatal risk factors nor associated with the currently promoted 'new' risk factors. Thermal insulation of the infant's bedding and clothing and excess thermal insulation (for any observed room temperature) were calculated. Bed sharing differed significantly between the groups as did the use of a sheepskin, tucking in firmly, the closing of doors and windows and the use of heating in the infant's room. After stratifying by bed sharing practice and season of interview, it was found that bed sharing infants had more thermal insulation than those sleeping alone irrespective of season of interview. Infants sleeping alone in the Asian-born and Southern European-born groups were kept warmer than infants in the other two groups. Cultural factors appear to affect the thermal environment in which infants are raised. Some bed sharing infants in all four groups were inappropriately warm, particularly in colder weather, but this was more likely in the Asian-born (low risk) group than in the home birth (high risk) group. These results do not explain the differences in SIDS incidence between the groups.     

Chronic fetal hypoxia and sudden infant death syndrome: interaction between maternal smoking and low hematocrit during pregnancy

To investigate the hypothesis that chronic fetal hypoxia contributes to the etiology of sudden infant death syndrome (SIDS), a possible interaction between the effect of maternal cigarette smoking and low hematocrit during pregnancy on the risk of SIDS was studied using the US Collaborative Perinatal Project cohort. The 193 SIDS cases identified in the cohort were analyzed with 1930 controls randomly selected from infants who survived the first year of life. After adjustment for maternal age, infants born to mothers who smoked 10 or more cigarettes per day and who were anemic (hematocrit less than 30%) during pregnancy were at a much higher risk of SIDS than infants born to mothers who did not smoke and were not anemic (odds ratio = 4.0; 95% confidence limits, 2.1 and 7.4). Smoking 10 or more cigarettes per day vs none increased the risk of SIDS by 70% among women with hematocrit at or above 30% but increased risk threefold among women with hematocrit below 30%. After adjustment for more potential confounders in a logistic regression model, the effect of smoking on SIDS continued to increase with lower levels of hematocrit during pregnancy. Birth weight accounted for very little of these associations. Low hematocrit was not a risk factor for SIDS among nonsmokers but became an important predictor among heavy smokers. These findings are in agreement with the hypothesis that chronic fetal hypoxia may predispose to SIDS, possibly by impairing the normal development of the fetal central nervous system.     

Head turning and face-down positioning in prone-sleeping premature infants

BACKGROUND: Term infants may die of sudden infant death syndrome (SIDS) when they assume the face-straight-down or the face-near-straight-down head positions. Preterm infants have a higher SIDS rate, but it is not known how often they assume the face-straight-down and face-near-straight-down positions. OBJECTIVES: To determine the frequency and cardiorespiratory consequences of head turning and face-down head positioning in prone-sleeping premature infants. STUDY DESIGN: Supervised overnight cardiorespiratory and audiovisual recordings were conducted in 15 prone-sleeping preterm infants nearing hospital discharge: birth weight, 1178 101 (SEM) g, postconceptional age, 40 1.0 weeks. RESULTS: The preterm infants, studied at a younger postconceptional age than previously reported term infants, seldom turned their heads during sleep; therefore they rarely assumed the face-straight-down position (6 episodes in 3 infants) or the face-near-straight-down position (30 episodes in 6 infants). CONCLUSIONS: Prematurely born infants, known to be at increased risk of SIDS, rarely assume face-down positions when sleeping prone at approximately 40 weeks' postconceptional age. These results suggest that head turning during sleep is developmentally regulated and may have relevance to understanding the age distribution of SIDS.