Why Back to Sleep is the Safest Position for Your Baby

Red Nose recommends: always sleep baby on the back.

Key Points on why Back to Sleep is safest:

  • Always place baby on the back to sleep and not on the tummy or side. There is an increased risk of sudden unexpected death for babies when they sleep on their tummies and there is a danger of rolling to this position if they are slept on their sides.
  • It is important that babies are always placed on the back to sleep. Babies who are usually slept on the back and are placed on the tummy or side for the first time are at an increased risk of sudden unexpected death.
  • Once a baby has been observed to repeatedly roll from back to front and back again on their own for several weeks, they can be left to find their preferred sleep position (this is usually around 5-6 months).
  • At the critical time of starting to roll it is very important that the sleep environment remains safe
  • Babies that can roll should no longer be wrapped
  • Babies born preterm should be slept on the back as soon as they are medically stable (out of oxygen).

Success of Back to Sleep Campaigns in reducing SUDI

In Australia, between 1989 and 2014, 4,808 babies died suddenly and unexpectedly (http://rednose.org.au/page/facts-and-figures). Baby deaths attributed to SUDI have fallen by 85% and it is estimated that 9,967 babies’ lives have been saved as a result of Red Nose’s baby safe sleeping campaigns. Evidence suggests that the marked reduction in incidence of babies dying suddenly and unexpectedly can be directly associated with Red Nose’s Australian public health campaigns which promoted safe sleeping practices, particularly advice given to parents to place their baby on their back to sleep1. These findings are consistent with international studies that have reported marked declines in SIDS in countries which have introduced similar public health campaigns to reduce known risk factors.2-5 In 2014 there were 54 SIDS deaths among the 113 SUDI deaths reported in Australia (http://rednose.org.au/page/facts-and-figures).

SIDS is a diagnosis of exclusion and there has been considerable research into the underlying mechanisms which may underpin the known risk factors for SIDS. SIDS has long been believed to be multifactorial in origin6 and a triple risk hypothesis has been proposed to model the current knowledge7 (see The Triple Risk Model for more details). This model proposes that SIDS may occur when a vulnerable baby, such as one born preterm or exposed to maternal smoking, at a critical but unstable developmental period in homeostatic control, is exposed to an exogenous stressor such as being placed on the tummy (prone) to sleep. The model further proposes that babies are more likely to die if all three factors occur simultaneously, and that the vulnerability lies dormant until they enter the critical developmental period and are exposed to an exogenous stressor. SIDS occurs during sleep and the peak incidence is between 2-4 months of age, when sleep patterns are rapidly maturing. The final pathway to SIDS is widely believed to involve immature cardiorespiratory control, in conjunction with a failure of arousal from sleep.2

The evidence for back sleeping being protective against SUDI

There is now conclusive evidence from many countries that sleeping babies prone significantly increases the risk of SUDI (In the late 1980s a peak in SIDS rates prompted several large scale case-controlled studies in a number of countries.8 These world-wide epidemiological studies consistently identified prone sleeping as the major risk factor for SIDS.9-16 In the prone compared to non-prone sleeping positions, the relative risk or odds ratio (OR) associated with SIDS ranged from 3.5 to 9.3.17 In Australia, the recommendation that babies should not be slept prone was made in 1991.18 In 1997 a second expert group recommended that babies be placed on the back to sleep and stressed that propping of babies on their sides should be avoided. These recommendations have been supported in most developed countries and implemented through targeted public health campaigns by national SIDS organisations such as Red Nose in Australia and New Zealand, The Lullaby Trust in the UK, First Candle in the USA.

Since the recommendation of putting babies on their back to sleep there has been, a rapid decline in SIDS mortality which has provided overwhelming evidence of the strong association between prone sleeping and SUDI.1,11,19-23

Studies have identified that the side sleeping position is unstable and many babies are found prone after being placed to sleep on their side. The risks of side and prone sleep positions were similar in magnitude (OR: 2.0 and 2.6 respectively), largely due to infants being placed to sleep on their sides, but found prone24 and the population-attributable risk for the side sleeping position is higher than the risk for the prone position due to a larger number of infants being placed on their side rather than prone to sleep.25-26

Babies who are unaccustomed to sleeping prone are particularly at risk in the prone sleeping position (adjusted OR: 8.7-45.4)24-27 Physiological studies have identified that babies inexperienced in prone sleeping have decreased ability to escape from asphyxiating sleep environments (environments which may block their airway or reduce the ability to breathe) when placed prone.28

Concerns about back sleeping

Risk of aspiration or choking

Some parents and health professionals have expressed concern about back sleeping and the risk of a baby choking in this position. However, careful study of the baby airway has shown that healthy babies placed to sleep on the back are less likely to choke on vomit than prone or tummy sleeping babies.29 In the supine position the upper respiratory airway is above the oesophagus (digestive tract). Therefore, regurgitated milk ascending the oesophagus is readily swallowed again such that aspiration into the respiratory tract is avoided. When the baby is placed on the tummy, the oesophagus sits above the baby’s upper airway. If the baby regurgitates or vomits milk, it is relatively easy for the milk or fluid to be inhaled into the baby’s upper airway leading to micro-aspiration and stimulating receptors leading to cessation of breathing (apnoea).29 Several studies have now shown that the risk of aspiration is not increased by supine sleeping.30-32

There is often particular concern regarding aspiration in babies with gastro-oesophageal reflux. The AAP supports the recommendations of the North American Society for Pediatric Gastroenterology and Nutrition which recommends that babies with gastro-oesophageal reflux be placed in the supine position to sleep. In babies with particular rare medical conditions for whom the risk of death from gastro-oesophageal reflux is greater than the risk of SIDS medical practitioners may provide specific advice on sleeping position.33 Elevating the head of the cot while the baby is sleeping supine is not effective in reducing gastro-oesophageal reflux.34-35 In addition, elevating the cot can result in the baby sliding underneath the bedding and is not recommended.36 Pillows or positional devices that position the baby with an elevation and are often marketed for baby reflux, are not recommended due to the risks of suffocation and lack of evidence supporting efficacy.

Positional plagiocephaly

An increase in skull deformity (deformational plagiocephaly and craniosynostosis) requiring treatment has been reported since the Back to Sleep campaign.37 This is reported to be related to the concern that parents had in placing their baby on their tummy at any time, resulting in babies spending long periods of time on their back. In order to reduce the likelihood of skull shape problems, parents are encouraged to place babies prone for ‘tummy time’ from birth when babies are awake and under direct supervision. However, another earlier study demonstrated that there was no significant relationship between supine sleeping and the development of plagiocephaly; the baby’s positional preference and baby care practices used by parents including the frequency of supervised tummy time, played a greater role.38 [For further information about positional plagiocephaly and tips for tummy time see Baby’s Head Shape]

My baby sleeps longer and more deeply on their tummy

Many parents and grandparents report that the baby appears to sleep longer when on the tummy. This is thought to be due to reduced arousal responses.29,39-44 However, arousal and swallowing mechanisms are needed to protect baby’s airway and work best when a baby is placed to sleep on the back.

The back sleeping position is best for newborn babies

Some health professionals and parents continue to place newborn babies on the side immediately after birth in the belief that they need to clear their airway of amniotic fluid and are less likely to aspirate when in the side position. There is no evidence that fluid is more readily cleared in the side position.36 Babies should be placed on the back as soon as they are ready to be placed in the cot or bassinet. It is important that parents observe health professionals placing babies in the supine position as they are more likely to model this practice when they go home.45-48

The back sleeping position is best for preterm babies

Preterm babies are at increased risk for SUDI, including SIDS, compared to full term babies.49-51 Studies in the UK and New Zealand have reported that at least four times as many SIDS infants were born preterm compared to control infants who did not die (20% compared to 5%) and these proportional differences have remained unchanged since the introduction of public campaigns for reducing the risks.52-53 The association between the prone sleeping position and SIDS among low birth weight babies is equal to or stronger than that in babies born at term.27 It has been suggested that if the mothers of preterm or low birth weight infants followed the safe sleeping recommendations and all placed their infants supine in a cot by the parental bed, this would potentially reduce the overall SIDS rate by a further 20% 52.

Preterm babies are frequently placed prone as this position is thought to improve respiratory function and reduce energy requirements. It is common practice for babies requiring intensive care to be placed in the prone position during their acute illness. In one survey, approximately 95% of neonatal intensive care unit (NICU) nurses identified a non-supine position as the best sleep position for preterm babies. This study reported that nurses believed prone sleeping was beneficial for respiratory associated complications, such as upper airway anomalies and respiratory distress as well as non-respiratory complications, such as reflux and inconsolability.54 However, it is likely that these improvements are simply due to babies spending more time in quiet sleep and less time in active sleep, a state associated with increased apnoeas and increased arousability.55-56 The current recommendation is that preterm babies are placed supine as soon as clinically stable, i.e. out of oxygen, and as early as possible prior to discharge from hospital so that their parents are used to them sleeping in this position and are supported with settling their babies in the back sleeping position.

Likely protective mechanism of back sleeping

Body position during sleep significantly modifies both the spontaneous and induced arousals in preterm and term babies, with babies being significantly less arousable when slept prone.39-44 Indeed, it is this perceived deeper sleep that reinforces parents’ tendencies to prefer sleeping the baby in the prone position. Some studies have identified that babies sleep longer in the prone position and have increased quiet sleep, which is a state of reduced arousability.42 The prone sleeping position is associated with higher central and peripheral body temperatures when compared to the supine position.57-58 Cardiovascular control is also significantly altered in the prone sleeping position in both term and preterm babies. Compared to the supine sleeping position, heart rate in the prone position is increased during sleep in both term and preterm babies.40-42,59-63 Studies investigating heart rate variability, a measure of autonomic control of heart rate, have found that at both 1 and 3 months postnatal age, overall heart rate variability is decreased in the prone position during sleep in both term and preterm babies,41,61-62,64-67 suggestive of poor autonomic control in the prone sleeping position. It has been suggested that a reduction in parasympathetic control caused by an increase in peripheral skin temperature in the prone position may underlie the change in heart rate variability.65 Several studies have found that the sympathetic effects on blood pressure and vasomotor tone are decreased in the prone sleeping position.57,59,68-69 Lower resting blood pressure and altered blood pressure responses 57,68-69 and decreased vasoconstrictor ability59 to head-up tilting have been identified in term babies when sleeping in the prone position compared with the supine position. The prone position has also been associated with lower cerebral oxygenation in healthy term babies, a finding which may underpin the reduced arousal responses in this position.70 Studies have also shown that swallowing and arousal, which are essential mechanisms of airway protection, are also impaired in the prone position during active sleep,29 and were improved in the supine position. When challenged with simulated reflux or postnasal secretions breathing rate was significantly reduced when infants slept prone.

The supine or back sleeping position is the safest position for babies to sleep for the first 12 months of life.

The Red Nose Safe Sleeping program is based on scientific evidence and was developed by Australian SUDI researchers, paediatricians, pathologists, and child health experts with input from overseas experts in the field. The 85% drop in SUDI deaths and the 9,967 lives that have been saved is testament to the effectiveness of the program.

For further information phone Red Nose on 1300 998 698.

Suggested citation

Red Nose. National Scientific Advisory Group (NSAG). (2016). Information Statement: Why Back to Sleep is the Safest Position for Your Baby. Melbourne: Red Nose. The first edition of this information statement was posted in August 2016.

View the references for this article here.

Last modified: 27/2/18