Becoming a parent comes with lots of excitement but it also brings many new questions and decisions! None perhaps more important than deciding a sleeping arrangement for after the little one arrives. And, as with all parenting decisions, the more important a decision is, the more diverse and passionate the opinions are. Often the advocates of two approaches choose evidence selectively to support one over another. So, it’s easy to feel a bit confused.
But what does the evidence really say about this? To make an informed choice about whether to co-sleep or not, and to answer the question 'is co-sleeping safe for my family?', parents need to understand evidence for two questions:
- Are both the choices equally safe?
- Do babies sleep longer or better with one method?
We've looked at the main research findings and drawn out the important conclusions.
The term co-sleeping is interchangeably used with bed-sharing and room-sharing by different researchers. To avoid confusion, it’s advisable to use the terms bed-sharing and room-sharing, which are much clearer. So, before we look at what research says about the different choices, let’s clarify different names/terms that often gets used:
- Room-sharing: This is when baby sleeps in the same room as parent. More technically – it refers to a sleeping arrangement where parent and baby sleep nearby on different surfaces in the same room – such as baby sleeping in a separate bed or cot, often next to parent's bed. At times, the cot’s side could be lowered providing easier access to baby.
- Bed-sharing: Sleeping in the same bed as your baby. More technically – it refers to a sleeping arrangement where parents and baby sleep in close proximity on the same surface.
- Solitary sleeping: A term often used for baby sleeping on their own in a nursery or separate bedroom.
In this first part, we discuss questions on safety and in the second part we will look at the impact on baby’s sleep and parent's sleep with a co-sleeping and solitary sleeping arrangement.
Are both choices equally safe?
The most important debate about the safety of co-sleeping is centred around Sudden Infant Death Syndrome (SIDS). SIDS is the sudden, unexplained death of a child of less than one year of age – often during sleep. Its diagnosis requires that the death remains unexplained even after a thorough autopsy and detailed death scene investigation. Thankfully, the number of babies dying of SIDS have seen a dramatic reduction (~50% – 85%) since the 1990s – this reduction has been mainly attributed to advice to put the babies to sleep on their backs (supine position) and not on their tummies (prone position). However, this decline has tailed off over the last few years. Some of the early studies on SIDS identified a correlation between bed-sharing and SIDS. However, more recent studies found that these older studies did not fully account for other risk factors.
So, what do the research findings suggest?
Many of the older studies and some of the more recent studies that don’t look at other risk-factors linked with SIDS and find higher association of SIDS with bed-sharing [1, 2]
The studies that control for other risk factors that could cause SIDS have mainly concluded that, in absence of specific risk factors, there is no clear evidence for significantly higher rates of SIDS with bed-sharing [3, 4, 5]. One of these studies by Blair et al  noted that “The Back to Sleep campaign, initiated in the UK in 1991, advising parents to avoid placing infants in the prone position for sleep has had a dramatic effect on the number of SIDS deaths occurring in a cot but less effect on co-sleeping deaths which now account for 30–50% of all SIDS deaths. Previously we have demonstrated that a proportion of these co-sleeping deaths occurred while the parent and infant slept on a sofa or chair as well as a significant interaction between co-sleeping and parents recently consuming alcohol or drugs”. This highlighted that bed-sharing has important correlation with SIDS, however in many cases this bed-sharing is associated with other risk factors. In the same paper – authors concluded that “An important implication of our findings is that to give blanket advice to all parents never to bed-share with their infant does not reflect the evidence”. 
A meta-analysis study done by Vennermann et al on bed sharing and risk of SIDS concluded that bed-sharing is a risk factor for SIDS particularly for very young infants, and in smoking parents. However, the authors of the study acknowledge that, as some of the older studies included did not fully take into account the association with other risk factors, the results of meta-analysis also have some limitation. 
(A meta-analysis is a study where researchers look at all previous studies on a particular topic that meet their criteria and then use statistical procedure for combining data from all those studies. One can call it a study of studies. So, results of meta-analysis are generally considered very credible. Of course, the meta-analysis is only as good as the studies that are included as part of analysis).
The role of breastfeeding as having a protective effect on SIDS has been a matter of debate with some studies supporting the protective effect and other studies that took into account other associated factors concluding that breastfeeding in itself was not protective. However, a recent review report based on a meta-analysis and a recent German Study of Sudden Infant Death have found that breastfeeding (particularly exclusive breastfeeding) significantly lowered risk of SIDS, with the German study concluding that exclusive breastfeeding at 1 month of age reduced SIDS risk by half. [10, 12, 13, 14]
- Two main factors are thought to contribute to this effect of breastfeeding – 1) Breastfed infants are more easily aroused from sleep compared to the babies that are formula-fed, and 2) Breastfeeding boosts the immune system and therefore reduces the risk of infections that raise the risk of SIDS 
- Some experts and organisations have argued that bed-sharing is more conducive to breastfeeding and possibly promote a longer period of breastfeeding. And given that breastfeeding itself is protective for SIDS, bed-sharing would also be beneficial. However, others argue that bed-sharing is not necessary for breastfeeding and one study found no difference in rate of SIDS for breastfed and non-breastfed babies that shared bed with their mother. [16, 17, 18]
What are the key risk factors for SIDS associated with bed-sharing?
Different studies have identified some key risk factors associated with bed sharing. [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11].
- The risk of SIDS in bed-sharing is much higher (up to 10 times) in babies less than 12 weeks of age, and some studies show that the risks of SIDS with bed-sharing in younger infants persists even when parents don’t smoke.
- Prone and side sleeping positions significantly increase the risk of SIDS.
- Parental smoking (particularly smoking by mother) significantly increases the risk of SIDS with bed-sharing. Also, those babies whose mother continued to smoke during pregnancy are also considered at increased risk of SIDS.
- Parents (or bed-sharer) having drunk alcohol or used drugs, or are over-tired, increase the SIDS risk as these things could lead to them not being able to respond to baby’s distress, or they may accidentally turn over, leading to baby’s mouth and/or nose being covered
- ‘Bed-sharing’ in a sofa and/or chair increases SIDS risk – this appears to be mainly due to a) this is likely to be more unplanned or accidental as the parent might have gone to sleep with baby without intending to due to either alcohol or drug use or being over-tired, and b) the smaller size may increase the risk of baby’s mouth and nose accidentally being covered
- Head-covering, soft bedding accessories – blankets, stuffed toys, comforters or pillows being used in the sleeping area – also increase the risk of SIDS when bed-sharing. Studies also noted that these risk factors are more common when bedsharing compared to solitary-sleeping.
- Overheating, being more heavily wrapped, the use of duvets (particularly ones with higher tog, > 8 tog), having the heating on all night also increases the risk of SIDS.
- Multiple-bed sharers also increases the risk of SIDS.
- Bed-sharing occasionally rather than routine bed-sharing appears to increase the risk of SIDS. Meta-analysis authors Vennermann et al note that – "bed sharing during the last night when bed sharing was not routine increased the risk two-fold.” They also noted that “this category largely comprises sick infants, who may be more likely to be taken to bed for comfort and that the disease status rather than the bed sharing itself increases the risk of SIDS… and infants who are returned to their own cot during the middle of the night are not at an increased risk of SIDS”. So, temporary bed sharing for the purposes of feeding and comforting does not bring added risk.
And what does the recommendation from different professional bodies say about bed-sharing?
In US, The American Academy of Pediatrics Taskforce report recommends room sharing without bed-sharing. . Their report mentions that “there is evidence that this arrangement decreases the risk of SIDS by as much as 50% and is safer than bed-sharing or solitary sleeping (when the infant is in a separate room). In addition, this arrangement is most likely to prevent suffocation, strangulation, and entrapment, which may occur when the infant is sleeping in the adult bed. Furthermore, room-sharing without bed-sharing allows close proximity to the infant, which facilitates feeding, comforting, and monitoring of the infant.” The report further comments that “epidemiological studies have not found bed-sharing to be protective against SIDS and accidental suffocation for any subgroups of the population. It is acknowledged that there are some cultures for which bed-sharing is the norm and SIDS rates are low, but there are other cultures for which bed-sharing is the norm and SIDS rates are high…The task force, therefore, believes that there is insufficient evidence to recommend any bed-sharing situation in the hospital or at home as safe.”
In the UK, the NICE Guidelines on co-sleeping and SIDS recognises that there is an association between co-sleeping and SIDS but not a causal relationship i.e., co-sleeping does not cause SIDS. The guideline recommends that parents should be informed of the association between co-sleeping and SIDS and about the higher risk when parents smoke, with recent alcohol or drugs use, and low birth weight or premature babies.
Now, for some main simple messages for sleep-deprived parents with baby brains
- The first thing to remember is that fortunately SIDS is very rare occurrence. In UK, the rate of SIDS is 0.3 deaths per 1000 live births. Rates of SIDS deaths have reduced over the last two decades.
- Like with most decisions you make regarding your baby, after considering all the information and advice, you need to consider what works best for you and your baby, but bear in mind, there are some clear dos and don’ts.
- Room-sharing with baby sleeping in a bassinet, moses basket or a cot in the parents’ room in first 6 months is safer than bed-sharing as it reduces the risk of SIDS (by up to 50%).
- Bed-sharing has higher association with SIDS particularly when combined with other risk factors and therefore, should be avoided if:
- You or your partner smoke
- You or your partner have used alcohol or drugs
- Your baby had a low birth weight (less than 2.5 kg) or was born premature (born before 37 weeks of pregnancy)
- Sleeping with your baby on sofa or chair should be avoided
- Generally, occasional or accidental or unplanned bed-sharing should be avoided. If you do need to bring your baby into the bed for breastfeeding or settling him down, then it's best to return him back to his cot or bassinet at the earliest.
- If you do choose to bed-share regularly (being aware of the association with SIDS), then its best to ensure that the sleep area is as safe as possible
- Ensure that none of the high risk factors mentioned above are true
- The bed surface is firm
- There are no soft-bedding materials – loose blankets, soft-toys etc. that can cover your baby’s face or head in the sleeping area
- Avoid baby getting too hot by using appropriate heating control
- Of course, other safe sleeping advice – always putting baby to sleep on their back, keeping their head uncovered, and using ‘feet to foot’ position should be followed
We hope the above information provides a good overview of the evidence and debates around the question 'is co-sleeping safe?'. However, this is just one half of the story! In the second half, we will look at what the evidence says about the impact of co-sleeping on baby’s sleep routine.
Here are the links to the key studies. We have looked at more studies but have referenced only the main ones:
- Bed sharing is more common in sudden infant death syndrome than in explained sudden unexpected deaths in infancy – Mollborg et al, August 2015, Acta Paediatricia; https://www.ncbi.nlm.nih.gov/pubmed/18450800/
- Sudden infant death syndrome, bedsharing, parental weight, and age at death – Carroll-Pankhurst et al, March 2001, Pediatrics
- Bed-sharing in the absence of hazardous circumstances: Is there a risk of SIDS? – Blair et al, PLOS ONE, September 2014; http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0107799
- Hazardous cosleeping environments and risk factors amenable to change – Blair et al, British Medical Journal, October 2009; https://www.ncbi.nlm.nih.gov/pubmed/19826174
- Bed sharing and the sudden infant death syndrome – Klonoff-Cohen et al, British Medical Journal, November 1995; https://www.ncbi.nlm.nih.gov/pubmed/7496236/
- Bed sharing and the risk of sudden infant death syndrome: can we resolve the debate? – Vennermann et al, The Journal of Pediatrics, January 2012; http://www.jpeds.com/article/S0022-3476(11)00680-9/fulltext
- Interaction between bedding and sleeping position in the sudden infant death syndrome: a population based case-control study – Fleming et al, July 1990, British Medical Journal; https://www.ncbi.nlm.nih.gov/pubmed/2390588?dopt=Abstract
- Head covering – a major modifiable risk factor for sudden infant death syndrome: a systematic review – Blair et al, Archives of Diseases in Childhood, September 2008; https://www.ncbi.nlm.nih.gov/pubmed/18450800/
- Sleep environment risk factors for sudden infant death syndrome: the German Sudden Infant Death Syndrome Study – Vennemann et al, Pediatrics, April 2009; https://www.ncbi.nlm.nih.gov/pubmed/19336376/
- SIDS and Other Sleep-Related Infant Deaths: Expansion of Recommendations for a Safe Infant Sleeping Environment – American Academy of Pediatrics, Pediatrics, November 2011; http://pediatrics.aappublications.org/content/128/5/e1341.full#xref-ref-158-1
- Environment of infants during sleep and risk of the sudden infant death syndrome: results of 1993-5 case-control study for confidential inquiry into stillbirths and deaths in infancy – Fleming et al, July 1996, British Medical Journey – http://www.bmj.com/content/313/7051/191.full.print
- Risk factors for sudden infant death syndrome following the prevention campaign in New Zealand: a prospective study – Mitchell et al, Pediatrics. 1997;100(5):835–840
- Sleep environment and the risk of sudden infant death syndrome in an urban population: the Chicago Infant Mortality Study – Hauck et al, Pediatrics. 2003;111(5 pt 2):1207–1214
- Ip S, Chung M, Raman G, Trikalinos TA, Lau J. A summary of the Agency for Healthcare Research and Quality’s evidence report on breastfeeding in developed countries. Breastfeed Med. 2009;4(suppl 1):S17–S30
- Breastfeeding and reduced risk of sudden infant death syndrome: a meta-analysis, Hauck et al, Pediatrics. 2011;128(1):103–110
- Infant-parent co-sleeping in an evolutionary perspective: implications for understanding infant sleep development and the sudden infant death syndrome, McKenna et al, April 1993, Sleep; https://www.ncbi.nlm.nih.gov/pubmed/8506461
- Bed-sharing in the first four months of life: a risk factor for sudden infant death, Ruys et al, Acta Paediatricia. 2007;96(10):1399–1403
- Factors associated with the duration of breastfeeding, Vogel et al, Acta Paediatricia. 1999;88(12):1320–1326
- NICE co-sleeping and SIDS guidelines; https://www.nice.org.uk/guidance/cg37/chapter/1-Recommendations
Other useful resources:
- Lullaby Trust, which is a UK based charity that specifically aims to reduce SIDS deaths – https://www.lullabytrust.org.uk/professionals/promoting-safe-baby-care-2/
- NCT website – https://www.nct.org.uk/parenting/co-sleeping-safely-your-baby