Is "co-sleeping" (infant sleeps in bed with parents) safe?

Question

Among some circles, co-sleeping is highly advocated for newborns/infants due to ease of breastfeeding and potential developmental bonding to the mother (for more examples, read about proposed advantages here). The immediate and obvious red flag that came to mind was rolling over one's baby. A defense I've heard is that you... just won't:

[In response to inquiry about the safety of co-sleeping] You won't squash him. You couldn't even comfortably roll onto a teddy bear in your sleep, let alone your own baby that your subconscious is ALWAYS aware of. (source)

you wont roll onto your baby. there is no way you forget they are there even when you're dead to the world. (source)

Physically and psychologically it is HIGHLY unlikely that you will roll over onto your baby when co-sleeping. It’s an evolutionary, parental instinct sorta thing (don’t remember the exact name for this but definitely learned about it in my psych classes). Essentially as a parent your conscious and unconscious self is aware that protecting your baby is a priority and you won’t smush or smother them. (source)

However, according to the Consumer Product Safety Commission, via Kid's Health:

According to the CPSC, at least 515 deaths were linked to infants and toddlers under 2 years of age sleeping in adult beds from January 1990 to December 1997:

• 121 of the deaths were attributed to a parent, caregiver, or sibling rolling on top of or against a baby while sleeping
• more than 75% of the deaths involved infants younger than 3 months old

Here's another pro-co-sleeping advocate (emphasis mine):

At the University of Notre Dame's Mother-Baby Behavioral Sleep Laboratory, our studies of breastfeeding mothers who sleep with their 2- to 4-month-olds reveal that both mothers and their babies are extremely sensitive throughout the night to each other's shifting position in the bed.

During my many years of studying sleep-sharing, I've never heard of a single instance in which, under safe conditions, it was proven that a mother suffocated her child. Notice that I said safe conditions: Babies can and do accidentally suffocate when one or both parents doesn't know a baby is in the bed, is drunk or desensitized by drugs, or is indifferent to the baby's presence.

So, to follow in the vein of the last bit:

Is co-sleeping safe when parents are aware of the baby's presence, are not under the influence of substances, and are not indifferent to the baby's presence?¹

In layman's terms: is co-sleeping safe under normal conditions?

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¹ Is that criterion last just a catch-all no true Scotsman variant? If the first two conditions aren't true then the parents must have been indifferent at some level?

Answer 1

No.

Co-sleeping is unsafe, particularly when compared to placing a child into a suitable cot / crib. Most of this risk comes from the bed and bedding not being suitable for infants, but suffocation by overlying is also a significant risk.

The only safe place for an infant to sleep is on its back in a crib/bed that meets relevant standards.

A retrospective review of death-scene and medical reports for SIDS and related deaths showed that children sleeping in adult beds increases their risk of death by at least a factor of 20:

Using cribs as the reference group and adjusting for potential confounders, the multivariate ORs showed that ... the risk of suffocation was approximately 40 times higher for infants in adult beds compared with those in cribs. The increase in risk remained high even when overlying deaths were discounted (32 times higher) or the estimate of rates of bedsharing among living infants doubled (20 times higher).

Instances of overlying (suffocation by a person sharing the bed) were rare, and the data is not as conclusive:

The diagnosis by medical examiners and coroners that overlying of an infant while sharing an adult bed was the “cause of death” remains controversial. More overlying deaths were reported by medical examiners and coroners in the 1990s (70 deaths) than in the 1980s (7 deaths). In approximately 40.3% of the cases (31 of 77), the narratives reported that a third party found the infant covered by an adult or a child, there were compression marks on the infant, or other findings suggesting the likelihood of overlying (eg, infant sleeping in twin bed with 2 adults). In both decades, overlying deaths were associated with very young infants, with an average age of 1.9 months. Only 1 overlying death occurred after 6 months of age, a report of a 10-month-old found with another child over him.

That said, this is not the major risk with co-sleeping, it's suffocation by other means - bedding, soft mattresses, a child getting wedged between the headboard/footboard/bedframe and the mattress.

Another population-based death-scene study of SIDS and related deaths found that for their selected records (all sleep-based deaths of children under two in a particular geographical area), nearly half involved bed sharing:

Deaths Occurring While Sharing a Bed or Other Sleep Surface

Nearly one half (56) of the infants (47.1%) died while sharing a sleep surface with one or more bedmates (1.4 ± .7; range: 1–4 bedmates; Table 3). For the majority, deaths while bedsharing were diagnosed as SIDS, but for 13 the diagnoses were suffocation or undetermined (23.2% of bedsharing deaths). All deaths occurred on sleep surfaces that were not designed specifically for infant sleep. In 13 cases (23.2%), the scene investigation showed evidence for entrapment of the infant, either by a bedmate or by the sleep surface. In 18 cases (33.0%), the bedsharing infant was found dead on a pillow or comforter, items specifically identified in earlier studies as bedding that increases risk for sudden death when used by infants.18,36,38 The pillows and comforters were on the shared sleep surface and the infant had been placed on top of them.

Controlling for smoking is also an important factor when assessing the risks of bedsharing, but it appears there is a definite effect when this is taken into account:

The impact of bedsharing on risk for sudden infant death remains controversial. Three case–control studies suggest that bedsharing increases risk for sudden death,24,26,45 but the risk is lessened when the high rate of maternal smoking in these studies is considered. In England, in particular, the rate of smoking among mothers whose infants died while bedsharing is so high that the risk for nonsmoking mothers cannot be calculated from the data.24 In the United States, a case–control study27 from Washington, DC showed increased risk especially when black infants bedshare. Finally, preliminary results from the Chicago Infant Mortality Study, a large, recent case–control study, strongly indicate an effect of bedsharing that is independent of smoking. 46 There are no recent published results addressing risk for infants sleeping alone outside of cribs, but data from the US Consumer Products Safety Commission suggest that the risk may be high...

With specific regard to alcohol consumption and bed sharing, a nationwide case-control study in New Zealand found that maternal alcohol consumption did not increase the risk of death while bed sharing, though it should be noted that there doesn't appear to be any conclusive research on this matter - there are studies whose conclusions are directly contradictory.

Neither maternal alcohol consumption nor the thermal resistance of the infant's clothing and bedding interacted with bed sharing to increase the risk of sudden infant death, and alcohol was not a risk factor by itself.

CONCLUSION--Infant bed sharing is associated with a significantly raised risk of the sudden infant death syndrome, particularly among infants of mothers who smoke.

Answer 2

I think it's worth providing an alternative viewpoint to this question.

Outside of the Western, developed world co-sleeping is the standard way for parents to sleep with young children, not the exception.

This article's fonts makes me want to burn my eyes out, but the final paragraph has a very interesting graphic created from NIMH data:

In China, where I live, co-sleeping is so common as to be the assumed situation. To do otherwise is strange and discussion-worthy.

This NYT article from 2007 says data is inconclusive.

Another article mentions author Margot Sunderland quoting:

“In the UK, 500 children a year die of Sids,” Sunderland writes. “In China, where it [co-sleeping] is taken for granted, Sids is so rare it does not have a name.”

She seems to have decent credentials.