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Science review: Is co-sleeping safe? (part II)

One of the biggest challenges that new parents face is lack of sleep, and it’s natural to just focus on how your new born is sleeping, putting your needs on the back-burner. Finding a healthy balance between keeping your baby safe and sound while avoiding sleep deprivation yourself is problematic for many parents.

There is clear, growing evidence that highlights the importance of sleep, so it’s not surprising that parents worry about it, a lot. Sleep is highly important for many different reasons, such as the healthy growth and development of your baby, avoiding maternal depression and other negative health aspects [1,2].

In our previous post, we discussed the research behind how different sleeping arrangements affect your baby’s safety, with a focus on avoiding SIDS (sudden infant death syndrome). We spoke about three different types of sleeping arrangement:

  • Room-sharing: baby sleeps in the same room as parent, on a different surface (such as in a cot)
  • Bed-sharing: baby sleeps on the same surface as parent (such as bed, sofa or chair)
  • Solitary sleeping: baby sleeps on their own in a separate nursery or bedroom

Deciding on which arrangement suits you and your baby can be difficult, so we’ve taken a look at the main research surrounding different sleeping arrangements and discussed how these impact you and your baby getting a good night’s sleep.

What do the research findings suggest?

Bed sharing may be easier for breastfeeding mothers

Every family is different, and you will find that what works for others might not work for you. Historically, bed-sharing has been commonplace in all societies. It allows for ease of natural mother-baby interactions, particularly with feeding. Although not all mothers are able to breastfeed, it is advisable to do it where possible as it provides many benefits, for mothers as well as babies [4,5].

Many studies have looked at the effects that bed-sharing has on mothers who breastfeed, and their babies [6]. Quillin & Glen [7] found that bed-sharing resulted in more sleep for breastfeeding mothers over those who bottle-fed. Kennedy et al [8] studied new mothers and the strategies they used to overcome sleep problems, and found that 40% of the mothers they looked at used bed-sharing to improve their own sleep. Bed-sharing means that mothers don’t have to get up to breastfeed, and the presence of a parent can soothe a baby, both of which can lead to increased sleep duration.

However, you must always consider your child’s safety when making your decisions on where they should sleep. The current recommendation from the UK Department of Health, the NICE Guidelines, the NHS and the American Association of Paediatrics is that, “The safest place for your baby to sleep for the first six months is in a cot in the same room as you.” [3]. If you do choose to bed-share, it’s especially important that you follow the NHS recommendations to keep your baby as safe as possible.

Do not use bed-sharing if you or your partner:

  • Smoke (even if you don’t smoke in the bed)
  • Have recently drunk alcohol or taken drugs
  • Have taken any medication that makes you sleep heavily

Do not use bed-sharing if your baby:

  • Was premature (born before 37 weeks)
  • Had a low birth weight (less than 5.5lb)

Never sleep with your baby on a sofa or chair, and always make sure that your baby sleeps on their back with no loose blankets, pillows, toys, etc. around in a room that isn’t too hot or too cold (18˚c is ideal).

Moving on from room-sharing to solitary sleeping

As 90% of SIDS occur in the first six months after birth, it has been advised that babies are kept close to parents for the first six months through room-sharing rather than bed-sharing. Room-sharing is the safest arrangement at this stage as it allows parents to be aware of signs of SIDS, but it doesn’t put the baby in danger from things such as accidental suffocation, which can happen with bed-sharing. However, there are no clear guidelines on what the best arrangement is beyond six months. Of course, most parents (where feasible) do eventually wish to move the baby to separate room at some point. Again, there is no right or wrong way; it’s down to your own preference.

There are number of studies that have looked at the impact of room-sharing vs. solitary sleeping on baby and parents’ sleep. In general, the studies we reviewed suggest that solitary sleeping can result in babies waking up less frequently at night-time. It also provides them with better self-soothing abilities meaning they can go back to sleep without their parents’ intervention.

The longer you wait, the more difficult it can get to move to solitary sleeping

A study by Penn State University found that, “Infants begin to experience separation anxiety in the second half of the first year, making it problematic to change sleep locations at that stage. Waiting too long can have negative effects on sleep quality for both parents and infants in both the short and long term.” [9]. For example, at nine months old, babies who learned to solitary sleep by four months slept for, on average, 1 hour and 40 minutes longer than babies who were still co-sleeping. This shows that, although it may be difficult to switch to solitary sleeping, the arrangement can improve your baby’s sleep in the long run.

Bed time routines and self-soothing

Parenting experts don’t agree on many things, but everyone agrees how important it is to have a good bed time routine. Sadeh & Anders look at the importance of bedtime routine, focused around a number of different studies [10]. One study by Adair et al found that, “Nine month old infants whose parents were present while the infant was falling asleep were significantly more likely to wake at night than infants whose parents were not present.” And another study by Johnson found that, “Eighty percent of infants who fell asleep on their own were sleeping through the night compared to less than one third of the infants who were soothed to sleep by their parents.”

Although it may be difficult to leave you baby to fall asleep on her own rather than being rocked or comforted, these studies show that it allows them to learn how to self-soothe and fall asleep alone. Thus, they do not interrupt their parents’ sleep as much.

Self-soothing behaviour can be achieved in all sleeping arrangements, but research suggests that it is easier to achieve in solitary sleeping as, if a parent is in the room, it is more difficult for babies to self-soothe and more difficult for parents to resist soothing their baby. So, it’s no surprise that solitary sleeping has been found to be more helpful for babies to learn to self soothe. Burnham et al [11] studied the sleep-wake patterns of solitary-sleeping babies in their first year and found three main variables that promote self-soothing: “Decreasing amounts of time spent out of crib across the first year, high levels of quiet sleep at birth, and longer parental response times to infant awakenings at 3 months.”

Self-soothing should not be confused with leaving a baby to “cry it out”. Whilst the “cry it out” method has its advocates, there are concerns that it can have negative effects [12] and is also emotionally hard on parents. Self-soothing can be achieved without leaving them to cry for long periods of time, such as by using “fading methods” (camping out and timed check-ins) [13].

Overtime, self-soothing can result in healthier sleep-wake patterns for children, including regular bedtimes which can support other aspects of daily life – giving parents a little bit of extra time to focus on their own wellbeing.

Remember: neither of the sleeping arrangements are intrinsically ‘good’ or ‘bad’ for baby’s sleep, so it is important to find the safest and healthiest arrangement that works for you and your baby.

Main messages from these findings

First, let’s reiterate again, there is no right or wrong way when choosing your sleeping arrangement – choose the one that appeals to you and works for you and your baby. Also, depending on your culture, family and friends, you may feel pressured to choose one method over other. For example, some parents in modern Western societies feel “judged” for bed-sharing and room-sharing beyond six months [14]. Make sure your decision is an informed choice and is based on what works best for you and your family.

Of course, be mindful that all the guidelines recommend that for the first six months, room sharing is the safest method and bed-sharing should be avoided to reduce the risk of SIDS. And, then when you and your baby are ready, you can switch to solitary sleeping. Some research suggests that earlier switch to solitary sleeping makes it easier and solitary sleeping can help with how your baby learns to self-soothe.


  • Bed-sharing has some practical advantages for breastfeeding mothers as you don’t need to get up to feed your baby, meaning a less disturbed night’s sleep
  • If you do choose to bed-share, you should follow safe sleep guidelines. Bed-sharing should be avoided if:
    • You or your partner smoke
    • You have used alcohol or drugs
    • Your baby has a low birth rate (less than 2.5kg) or was born premature (before 37 weeks of pregnancy)
    • You are sleeping on a sofa or chair

Room-sharing for the first six months

  • Room-sharing for the first six months allows you to respond to your baby faster and is recommended as parts of SIDS prevention guidelines
  • Although it’s important to be close to your baby, it’s also important to begin to establish independent sleeping to help your baby sleep better as it grows older by following sleep tips at the bottom of this page

Moving on to solitary sleeping

  • There is no clear recommendation for when to switch to solitary sleeping, but around six months is probably a good time to start, as it can become more difficult the later you leave it
  • Switching to solitary sleeping may be difficult for some parents and babies, so sleep training techniques such as camping out and timed check-ins could be helpful

Other sleep tips

  • Try to establish a consistent bedtime and routine
  • Lay your baby down on the bed before she falls asleep – letting her drift off to sleep on her own
  • Consider using a soft nightlight and lullabies or white noise as they can ‘condition’ your baby to know that it’s bedtime
  • Don’t rush in to soothe your baby at the slightest sound – let her learn to soothe herself. It’s possible that your presence could make her more alert and less likely to go back to sleep

We hope that this information, along with that in Science review: to co-sleep or not to co-sleep (part I) has helped to inform you on parent-baby sleeping arrangements. Remember, there is no one-size-fits-all arrangement, so do your research, use your instincts and find the safest, most comfortable arrangement for you and your little one.

Let us know in the comments below how you chose the right approach to you and how it worked out for you and your baby!


Here are the links to the main studies. We have looked at more but referenced only the main ones.

  1. Promoting and Protecting Infant Sleep – Allen, October 2013, Advances in Neonatal Care: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3439810/
  2. Sleep Deprivation: The Dark Side of Parenting – Callahan, May 2013, The Science of Mom: https://scienceofmom.com/2013/05/14/sleep-deprivation-the-dark-side-of-parenting/
  3. Your pregnancy and baby guide – NHS, September 2018: https://www.nhs.uk/conditions/pregnancy-and-baby/reducing-risk-cot-death/
  4. Quantifying the Benefits of Breastfeeding: A Summary of the Evidence – León-Cava et al, January 2002, The Pan American Health Organisation: http://s3.ennonline.net/attachments/421/bobcontents-and-introduction-summary.pdf
  5. A Well-Kept Secret: Breastfeeding’s Benefits to Mothers – Dermer, July 2001, New Beginnings: http://llli.net/nb/nbjulaug01p124.html
  6. What influences baby-sleeping behaviour at night? – Semple, April 2008, New Digest: https://www.nct.org.uk/files/related_documents/Research%20overview-%20Baby-sleeping-behaviour_1.pdf
  7. Interaction between feeding method and co-sleeping on maternal-newborn sleep – Quillin & Glenn, September 2004, Journal of obstetric, gynaecologic and neonatal nursing: https://www.ncbi.nlm.nih.gov/pubmed/15495703#
  8. Negotiating sleep: a qualitative study of new mothers – Kennedy et al, April 2007, The Journal of Perinatal and Neonatal Nursing: https://www.ncbi.nlm.nih.gov/pubmed/17505231
  9. Mom and baby sleeping in same room associated with less sleep, unsafe sleep habits – Penn State College of Medicine, June 2017, ScienceDaily: https://www.sciencedaily.com/releases/2017/06/170605102137.htm
  10. Infant Sleep Problems: Origins, Assessment, Interventions – Sadeh & Anders, Spring 1993, Infant Mental Health Journal: http://sleep.tau.ac.il/articles/Sadeh%20Anders%201993.pdf
  11. Nighttime sleep-wake patterns and self-soothing from birth to one year of age: a longitudinal intervention study – Burnham et al, September 2002, The Journal of Child Psychology and Psychiatry: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1201415/
  12. Dangers of “Crying it Out” – Narvaez, December 2011, Psychology Today: https://www.psychologytoday.com/gb/blog/moral-landscapes/201112/dangers-crying-it-out
  13. Baby sleep training: Fading methods – Hosley Steward, March 2016, Baby Center: https://www.babycenter.com/0_baby-sleep-training-fading-methods_10413749.bc
  14. Moms who co-sleep beyond six months may feel more depressed, judged – Penn State University, February 2018, ScienceDaily: https://www.sciencedaily.com/releases/2018/02/180228144434.htm