Co-sleeping (in the sense of bedsharing) advocates tend to pooh-pooh the idea that overlaying is a realistic hazard while sharing a bed with the baby, especially if you do it “safely”. Here’s James McKenna, the anthropologist who researches the physiological effects of bedsharing (but has, so far, not managed to prove any conclusive SIDS risk reduction as a result), on the subject:
In the worldwide ethnographic record, mothers accidentally suffocating their babies during the night is virtually unheard of, except among western industrialized nations, but here there are in the overwhelming number of cases, explanations of the deaths that require reference to dangerous circumstances and not to the act itself….
…While there is evidence that accidental suffocation can and does occur in bed-sharing situations, in the overwhelming number of cases (sometimes in 100% of them) in which a real overlay by an adult occurs, extremely unsafe sleeping condition or conditions can be identified including situations where adults are not aware that the infant was in the bed, or an adult sleeping partners who are drunk or desensitized by drugs, or indifferent to the presence of the baby.
It’s certainly true that under certain circumstances which constitute unsafe cosleeping – parents under the influence of drugs or alcohol, shared sleep on unsafe surfaces such as waterbeds or sofas – the chance of death from overlaying is far higher than in a safe cosleeping situation. I would also postulate that despite his physiological findings about cosleeping dyads, mothers who are fast asleep may still not be entirely “aware that the infant was in the bed”. But to claim that historically, no infants were ever overlain until the advent of western industrialized nations is complete rubbish.
Overlaying has been known at least since Biblical times (see I Kings 3:19 – remember the story about Solomon’s judgement between the two women and the baby? That’s what happened to the dead baby, according to the Bible). In fact, babies who died suddenly and unexpectedly were assumed until recent times to have been overlain – as cosleeping was common (and not only with parents). Undoubtedly, the overwhelming majority past events of infants dying in their sleep were actually SIDS, deliberate infanticide, or deaths as a result of undiagnosed congenital problems. But people attributed these deaths to overlaying, presumably, because such cases were known to happen (and they may not have been always wrong, mind – see this late 19th century cohort of infants in Dundee, Scotland). It’s also very hard to estimate deaths by overlaying (or SIDS deaths, for that matter) in tribal populations whose living membership may not exceed several hundreds or thousands at any given time, record keeping is scant, and where infant mortality (regardless of cause) is extremely common. Even in modern times and places, it’s often hard to discriminate between a SIDS death and an overlaying one; the coroner usually goes by the death scene investigation and the results of the autopsy (which may be negative in both cases). Ardent cosleepers often squawk that deaths from SIDS in adult beds are often misattributed to overlaying. Other than the preponderance of physical evidence, though, there is no way to determine this.
It’s certainly a stretch to say that every instance of infant overlay will cause the infant to die; After all, SIDS/SUDI death rates are measured per 10,000 population. But to pretend that it never happens, and when it does, it’s the fault of unsafe cosleeping, is equally a stretch (See my similar post on head covering as a SIDS risk factor).
A recent study in the Journal of Obstetric, Gynecologic, and Neonatal Nursing by Ateah et al helps shed some light on whether overlaying happens only when parents are under the influence or sleeping in unsafe conditions. Named “Maternal bedsharing practices, experiences, and awareness of risks”, the study’s aim was to determine the extent and experiences of bedsharing among mothers and their infants in the province of Manitoba, Canada, and the mothers’ knowledge of the accompanying risks.
Questionnaires were sent to all mothers giving birth in Manitoba in a given month (all 1,122 of them) when their babies were 3 months old; 293 of the mothers (26%) filled out and returned it. The questionnaire, besides collecting demographic data about the mothers and babies (age, baby’s gender, socioeconomic status, education, etc.), also asked about the mothers’ attitudes toward bedsharing and their agreement or disagreement with statements about the risks of bedsharing, and also – what is pertinent to this blogpost – whether they had, to their knowledge, rolled on to their infant in their sleep.
It’s interesting to note that the cohort who responded to the questionnaire was of higher socioeconomic status than the general population: nearly two thirds (66.2%) had completed higher education, the majority (over 90%) were married/partnered, and over 2/3 were at home with the baby at the time (either SAHMs or on maternity leave). Exceptions aside, this is not the demographic normally given to using illicit drugs or drinking to excess. Smoking was apparently not assessed. Over 2/3 also reported they were breastfeeding their infants, either exclusively or along with formula.
Among this high-status cohort, 42.7% shared a bed with their infant on a regular basis, and an additional nearly 30% slept with them occasionally. Ergo, almost 3/4 of the sample slept with their babies at one point or another. Of those who did, nearly 1 in 7 (13%) reported at least one incident involving someone rolling over fully or partially onto the baby while asleep. Comments offered included the following:
• “Yes, I’ve rolled onto my baby in my sleep. I woke myself up when I felt her. She didn’t move or cry. Thank goodness I’m a very light sleeper.”
• “Have found that my hand was partly covering the [baby’s] face as my initial intention was just to help hold paciﬁer in mouth . . . .”
• “With my second child, I woke up on top of her and the scary thing was that she wasn’t crying.”
• “Once I had him not on my arm, beside me. And I wasn’t aware and fell asleep hard andalmost rolled on him but [someone else] woke me up.”
• “I have not rolled onto my baby but my husband has. We had noticed a few times when
she was less than 1 month old, when we woke she was under the covers and very hot.”
• “I have slept with my baby maybe twice and both times he would wake me when he
moves. Once I turned over to ﬁnd that he had rolled slightly and a pillow was on top of
him. No more co-sleeping after that. ”
• “Yes, being a new mom is very exhausting, and I will occasionally fall asleep during
feedings, she will move or fuss if I am ‘squishing’ her. ”
While the events described did not cause the infants involved any harm, and in fact, some of the infants managed to alert the person who overlay them that they had to move, it’s clear that overlaying isn’t just some rare-to-nonexistent piece of fiction that some anti-bedsharing people (say, crib manufacturers) made up for their own personal gain, or something that only happens to mothers compromised by drugs or alcohol. Even if we assume the 74% of non-responders had no such events happen among them (something I find highly unlikely), there would still be an occurrence rate of roughly 1 in 40 parents (~2.5%) who experienced overlaying their infants. Just because in all the cases mentioned, the babies were not harmed (either because the mother, the baby, or a third person sensed something was wrong and prevented it), does not mean this will happen in every instance. So while death from overlaying on an adult bed is probably not a common event by any means, claiming it’s an impossibility or can only happen when a parent is compromised is, also, probably not likely, either.
Mind you, one of the rules for “safe cosleeping” also states you shouldn’t sleep with your baby if you’re “overly fatigued”. I’ve never quite understood how a parent is supposed to assess this correctly (indeed, the overly fatigued state, ironically, may hinder this assessment), nor have I ever actually heard any ideological cosleeper remove themselves from a bedsharing situation as a result. Maybe that’s why the authors of this study also agree that the safest sleeping environment for a small baby is on a sleeping surface adjacent to the parents’ bed, and state:
Since not all risk factors associated with bedsharing can be controlled, such as the level of caregiver exhaustion and infant overheating, recommendations for safe bedsharing
cannot be provided.