Press Release Re: Carpenter et al. Bedsharing Study

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My plan this weekend had been to enjoy a relaxing weekend away with the family.  However, Friday I was made aware of a new report coming out today on the “dangers of bedsharing”.  Needless to say, this weekend changed.  We were luckily able to view a copy of the article in advance and the group of researchers I have worked with on other posts and I wrote a response.  This is it.  It has been shared as a press release generally and given specifically to the BBC (the study is a UK one).  We shall see how the media responds in the days to come, but it’s nice to know that at least we’re not one step behind this time!

To view this in Portugese, click here.  Thanks to Andreia for the translation!

SIDS: Risks and Realities

We commend Carpenter et al (2013) for examining risks associated with incidence of SIDS but question their conclusions as unsubstantiated because of faulty and missing data, as well as confounding of criteria used to define bedsharing and risks—a challenge in any meta-analysis.

Their study examines some of the most salient risk factors for SIDS events—infant sleep position, parental use of cigarette smoking, infant birth weight and age. These risks have been well-documented as increasing risk of SIDS events. Thus, it is not surprising or informative to note that these factors remain risks in a re-evaluation of these findings.

While the risks examined do contribute significantly to increasing possibility of SIDS (see Chart 1 below), so do other factors such as bedding and temperature (see Box below for lists of risks not considered).  Without consideration of these risks, it is not possible to determine that one variable, such as bedsharing itself is inherently responsible for risk remaining in this study.  Nor is it possible to say that one of the variables within the nighttime care routine, such as breastfeeding, is not protective.

Chart 1. Adjusted Odds Ratios from Carpenter et al. (2013)

In addition to these major limitations in making broad, sweeping statements about risk based on this meta-analysis, there are two addition issues that are of significant concern in the paper as a whole. We address these herein.

The first is the treatment of breastfeeding.  Buried deep in the last section of the paper is the recommendation that breastfeeding be supported as a mechanism for protecting infant health, the construction of the hypotheses explored here lead to a very different framework. In attempting to examine whether breastfeeding is protective against risk of SIDS when parents bedshare seems to jumble the role of breastfeeding in a manner that undermines one of the stated objectives of the authors… to address health costs associated with early infant care by reducing SIDS events. Further the authors seem to overlook the AOR for bottlefeeding and SIDS risk (see Chart 2).

Chart 2. Adjusted Odds Ratios including bottlefeeding from Carpenter et al. (2013)

NOTE: BW = Birthweight

In examining the role of breastfeeding, the authors seem to overlook one essential aspect of infant development—breastfeeding contributes positively to both immediate and later infant health outcomes, not just a reduction in SIDS, though it serves as a protective factor there as well (Alm et al., 2002; Ford et al., 1993; Horne et al., 2004; McVea et al., 2000; Mitchell et al., 1992; Mosko et al., 1997; Scragg et al., 1993). Thus, important in consideration from any perspective is to encourage mothers’ breastfeeding through the infant’s first year of life. However, the authors seem to couch this protective factor in the arena of risk, thus confusing the message for practitioners and parents.

Instead of looking at how each of the variables in the dataset can contribute to risk of infants’ breathing or compromise arousal—the authors focus on whether the act of breastfeeding protects against all risk of SIDS. Clearly that is a standard that cannot be reached. We can, however, easily answer whether breastfeeding protects against SIDS regardless of parental behavior without the necessity of meta-analyses, the imputing of data from 5 of 12 variables, the compromising operational definitions of nighttime care contexts. The answer is simple, though not informative. Yes, there is still a risk. Why? Because there are multiple risk factors that compromise infants’ capacity to breath and infants’ ability to arouse. Breastfeeding does not vaccinate against all risks (e.g., pillow in the face).

The authors give lip service to breastfeeding, but suggest that any claim that bedsharing helps breastfeeding is ill-advised.  The use of the Netherlands as a key example of lowering bedsharing but increasing breastfeeding rates fails to make their point given the relatively low rates and low increases over the 10 year period discussed (a rise of 7% and 8% of any breastfeeding at 3 and 6 months respectively).  It is unclear if the strong anti-bedsharing campaign inhibited greater growth in breastfeeding, something that should be of concern when examining the costs associated with infant health.  In the US alone, a cost-analysis found that if we could get 80% mothers to breastfeed exclusively for six months (as the WHO recommends), the US would save $10.5 billion a year in health-related costs (Bartick & Reinhold, 2009).

Furthermore, it is misguided and dangerous to argue if bedsharing were recognized as a means of supporting breastfeeding, then we would see more SIDS events. Even more dangerous is to abandon support of breastfeeding in favour of supporting bottlefeeding if it were to detour bedsharing.  Although the AOR in the current meta-analysis suggests that bottle-feeding is a lower risk factor than bed-sharing (the validity of which will be discussed below), it only concerns itself with SIDS events, not the more general protective benefits of breastfeeding on infant health.  As previously mentioned, breastfeeding confers many health benefits, both immediate and long-term, to children (Horta et al., 2007; Ip et al., 2007; Martin et al., 2005; Owen et al., 2002) and to only consider SIDS events ignores the effects of lower breastfeeding rates on myriad other diseases.

The second issue pertains to the risk factors included and not included in the analysis.  The authors have thankfully confirmed some of the major risk factors associated with SIDS, both independently and when interacting with sleep location, such as sleep position, parent smoking, alcohol use, drug use, birth weight, and infant age.  The authors solidified many risks, as they were stated individually in the reports associated with each large data set. With this, researchers, practitioners, and parents now have a clear documentation of these specific risks. Very clearly presented is confirmation of known risks and quantification of those risks. For example, maternal smoking remains to be one of the most salient risks associated with SIDS—with paternal smoking contributing to risk as well. Similarly, infant sleep position (i.e., prone and side sleep), contribute significant risk of SIDS events.

Missing from the analysis are other known risk factors—specifically risk factors associated with the triple risk model either through environmental context (bedding) or infant vulnerability (prematurity).  Additionally, the authors fail to include data sets that do include these risk factors and come to very different conclusions about the inherent risk of bed sharing on SIDS events (e.g., Blabey & Gessner, 2009).  The authors argue that bed sharing is causally related to SIDS events via theories about infant breathing and arousability.  Specifically, the authors state, The proposition that bed sharing is causally related to SIDS is coherent with theories that respiratory obstruction, re-breathing expired gases, and thermal stress (or overheating),which may also give rise to the release of lethal toxins, are all mechanisms leading to SIDS, in the absence of smoking, alcohol or drugs. Infants placed prone are exposed to similar hazards.”

Is the implication in the press release for this article verifiable? Are breastfed, bedsharing babies at inherent risk of SIDS events? The answer is equally as simple, but much more informative. No.

Again what places an infant at risk of SIDS events is what places infants’ breathing and arousability at risk. The elements of the sleep context that place infants’ breathing and arousability at risk are well defined:

  • respiratory obstruction  (e.g., bedding)
  • rebreathing expired gases (i.e., from cover on face)
  • thermal stress through overheating (e.g., too many covers)
  • physiological vulnerability of arousal (e.g., deep sleep from formula usage)

These authors seem to be arguing that parenting behavior that can be associated with risk, even if the source of risk in not the behavior, should be stopped (i.e., bedsharing). This is problematic given that bedsharing is a universal, evolved practice, and is often preferred by parents. In fact, the absence of bedsharing does not eliminate risk of SIDS events. The diminishing of bedsharing however is associated with decreases in other behaviors shown to provide protection against SIDS events, such as breastfeeding.

Certainly, without question, a nighttime care context that includes bedsharing and breastfeeding can include elements that compromise infants’ breathing and ability to arouse. Importantly, we know that breastfeeding not only does not contribute to the risk, but serves to help reduce these risks.  See Chart 2 whereby bottlefed infants are at a greater risk of a SIDS even regardless of sleep location.

What of bedsharing per se?  The authors would have us believe bedsharing per se increases the risk of compromising infant breathing and arousability.  However, they fail to acknowledge or discuss the fact that there are other factors that influence breather and arousability such as bedding, temperature, and premature status (which is correlated with birth weight, but carries with it unique risk factors that must be considered).  Data from Alaska between 1993 and 2004 examined the same question of bed sharing risk, only they also included other known risk factors such as sleep surface (not just sofa, but the type of bed) and sleeping with a non-caregiver (Blabey & Gessner, 2009).  Additionally, the comparison group was taken from a state-wide monitoring system which does not focus on answering one day of bedsharing habits, but rather asks parents about usual bedsharing habits.  As such, they most likely had more accurate information on bedsharing than the studies included in the current review.  What was found in Alaska?  Of the SIDS events that took place while bedsharing, 99% included at least one risk factor, and thus the authors conclude that “infant bed sharing in the absence of other risk factors is not inherently dangerous”.

So, let’s stop going around in circles talking about secondary issues and focus on discussion on primary issue: decreasing the risk of SIDS events. If we want to decrease risk of SIDS events, then we must assure infants’ are in the best possible situation to support breathing and arousability.

How to do that?

Address Maternal and Infant Health that reduces risk:

  • Reduce vulnerability by reducing elements that contribute to vulnerability prenatally, i.e., intrauterine exposure to cigarette smoke, premature birth, stressful pregnancy with increased cortisol in blood stream, low birth weight, etc.
  • Reduce vulnerability postnatally by increasing health through breastfeeding, increasing proximity to parent during sleep to protect arousability, increase supportive contexts for new parents to support breastfeeding, infant health, maternal health, etc. This level of support will decrease infant vulnerability, increase infant health a capacity to arouse.
  • Increase maternal nutrition during pregnancy

Address Nighttime Care practices to ASSURE Breathing and Arousability

  • Place infants on back to protect breathing
  • Protect infants’ breathing and arousal by having infants sleep on firm, flat surface without pillows or toys or blankets
  • Protect infants arousal response by having a cool sleep environment absent blankets

Continued monitoring of sleep space

  • Keep infants in close proximity to parents to assure awareness of compromised breathing or arousal response that may be associated with unobservable variables, such as immature physiological responses

Despite a long history of efforts to reduce bedsharing, this nighttime care practice remains to be the preferred practice for many, is increasing in some areas, and provides many protective or health-benefiting outcomes for mothers and infants. Assuring infants’ safety at night is compromised when discussions shift from the criteria above to admonitions to sleep separately. A focus on protection and a discussion of what underlies risk will be much more successful in reducing risk of SIDS—as well as improving the health context postnatally.


Ten Important Variables Not Considered in The Carpenter et al. (2013) Paper
1 The researchers importantly did not consider whether the bedsharing was planned. Previous research from Venneman et al. (2009) showed no increased risk in planned bedsharing (versus unplanned). This is an incredibly important omission.
2 The paper did not consider the effects of the mother smoking during pregnancy, only smoking post birth. This is a missing risk factor.
3 Breastfeeding information is too limited to draw conclusions. No difference has been drawn between frequency and percentage of breastfeeds versus formula feeds for those ‘partially feeding’.
4 The paper only considered ‘illegal drug use’. Many postnatal mothers (0-12weeks after the birth) are prescribed analgesic medication for related birth induced injuries including but not limited to Caesarean healing, known to have a sedative effect. This was not considered at all.  This is a missing risk factor.
5 Prematurity was not considered at all. This is a missing risk factor.
6 Parental exhaustion was not considered at all. Some experts suggest this is considered to be less than 4-5 hours sleep in the past 24 hour period, other experts advise parents to use their instinct. Parental exhaustion naturally impacts on responsive to infant cues. This is a missing risk factor.
7 The researchers did not examine the effect of maternal (and paternal) obesity. This is a missing risk factor.
8 No differentiation was made between having one or both parents in the bed and importantly the location of the baby. It is advisable that the mother sleeps in between the father and infant. Equally it was not noted if older siblings were also present in the bed. This is a missing risk factor.
9 The researchers did not consider fully the impact of alcohol consumption by the father when bedsharing. This is a missing risk factor.
10 No mention was made of whether parents were aware of the risks of bedsharing and how to minimize these before sharing a bed with their infant.



Sarah Ockwell-Smith,

Professor Wendy Middlemiss, University of North Texas

Tracy Cassels, University of British Columbia,

Helen Stevens, Safe Sleep Space

Professor Darcia Narvaez, University of Notre Dame

Professor Kathy Kendall-Tackett, Texas Tech and University of New Hampshire


Selected References

Blabey, M.H., & Gessner, B.D. (2009). Infant bed-sharing practices and associated risk factors among births and infant deaths in Alaska. Public Health Reports, 124,527 -534.

Carpenter, R., McGarvey, C., Mitchell, E.A., Tappin, D.M., Vennemann, M.M., Smuk, M., Carpenter, J.R. (2013). Bedsharing when parents do not smoke: Is there a risk of SIDS? An individual level analysis of five major case-control studies. British Medical Journal Open, BMJ Open 2013;3:e002299. doi:10.1136/bmjopen-2012-002299

Ford RPK, Taylor BJ, Mitchell EA, et al. Breastfeeding and the risk of sudden infant death syndrome. Int J Epidemiol. 1993;22:885- 890

Horne RS, Parslow PM, Ferens D, Watts AM, Adamson TM. Comparison of evoked arousability in breast and formula fed infants. Arch Dis Child. 2004;89(1):22-25

Horta BL, Bahl R, Martinés JC, et al. Evidence onthe long-term effects of breastfeeding: systematicreview and meta-analyses. Geneva: World Health Organization; 2007:1-57.

Ip S, Chung M, Raman G, et al. Breastfeeding and maternal and infant health outcomes in developed countries. Evid Rep Technol Assess (FullRep). 2007;153:1-186.

Martin RM, Gunnell D, Smith GD. Breastfeeding in infancy and blood pressure in later life: systematic review and meta-analysis. Am JEpidemiol. 2005;161:15-26.

McVea KL, Turner PD, Peppler DK. The role of breastfeeding in sudden infant death syndrome. J Hum Lact. 2000;16:13-20

Mitchell EA, Taylor BJ, Ford RPK, et al. Four modifiable and other major risk factors for cot death: the New Zealand study. J Paediatr Child Health. 1992;28(suppl 1):S3-S8

Mosko S, Richard C, McKenna J. Infant arousals during mother-infant bed sharing: implications for infant sleep and sudden infant death syndrome research. Pediatrics. 1997;100:841- 849

Owen CG, Whincup PH, Gilg JA, et al. Effect of breast feeding in infancy on blood pressure in later life: systematic review and meta-analysis.BMJ. 2003;327:1189-1195.

Owen CG, Whincup PH, Odoki K, Gilg JA, Cook DG. Infant feeding and blood cholesterol: a study in adolescents and a systematic review. Pediatrics. 2002;110:597- 608

Scragg LK, Mitchell EA, Tonkin SL, Hassall IB. Evaluation of the cot death prevention programme in South Auckland. N Z Med J. 1993;106: 8 -10

Vennemann MM, Bajanowski T, Brinkmann B, Jorch G, Sauerland C, Mitchell EA.  Sleep environment risk factors for Sudden Infant Death Syndrome: the German Sudden Infant Death Syndrome study.  Pediatrics 2009; 123: 1162-70.

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  1. Sally says

    Thankyou for this. I woke up to this on the news this morning and my first thought was to check your site. I knew you wouldn’t let me down 😉

  2. Leah says

    Thank you for this.

    My question regarding the study is this:
    Is bed sharing in this study – all types of bed sharing ? Including the baby sleeping in a basinett in the parents bed?
    Or is it strictly babies cosleeping in the parents bed on the mattress with no basinett ?

    Do you know the answer ? I’d really like to know and believe if this wasn’t then into account for this study it should be.

    Thank you
    Ps is love a reply by email if you could take the time :)
    I’m a Mom to a 7 week old baby – first child.

    • Ahmie says

      in case no one replied, I’ll share my understanding. This was a meta-analysis, which means they took a bunch of research that was done before, and done in various ways, and tried to find common threads. Having read some of the source research, the questions you have aren’t consistently answered in the research that the authors of the meta-analysis had to base their study on. A lot of this research is done looking at death certificates and government investigations into infant deaths, and there isn’t consistency in what gets reported. Sometimes there isn’t even information on what the sleep surface was. It’s a VERY imperfect science. Dr. James McKenna has written quite a bit for non-academic readers and I strongly recommend starting with his work. You can start at – there are links to articles in the left sidebar.

  3. Ahmie Yeung says

    I was struck by the total absence of mention whether the breastfed babies were exclusively breastfeeding or not in the BBC article. My personal experience includes a pediatrician advising me to add rice cereal to my pumped milk when my 1st baby was under a month old so that he would sleep longer and more soundly in response to asking how often he was waking to feed at night (he was waking the normal every 4-5 hours at that point and I was not complaining at all because he was sleeping in my room – we weren’t yet confident enough to bedshare at that point, that came a few months later). My husband has sleep apnea and it runs in his family. This is also, as far as I can tell, an unexamined possible risk factor for SIDS (parental sleep apnea – if a parent has low rouseability, it may be genetic and increase the risk of SIDS for the baby). My husband’s apnea was the inspiration for co-sleeping, so I could sleep with a hand on the baby to feel him breathing. Four babies in I haven’t regretted a minute of it and I think I would have quit exclusively breastfeeding (and possibly entirely given up on breastfeeding) if we hadn’t been co-sleeping all along. I view the UK study as extremely irresponsible.

    • says

      That’s a wonderful point about parental sleep apnea! We should be including this in research!!! Thank you – I will mention this to some of the researchers doing this research more responsibly!

      • Ahmie Yeung says

        I am a budding researcher myself (I just completed my MA in Sociology this spring). Darcia knows how to reach me from my attending her conferences at ND, we’ve conversed via email off and on between and since. I would be happy to collaborate on and/or participate in research. My specific interests as a researcher are family sociology, medical sociology, and social psychology. I’m taking a break from academia to work on other projects while I decide if the PhD is really necessary. This kind of research is so hard to do in a prospective instead of retrospective way, and no one wants to add additional grief to families who are surviving the loss of a child so it is hard to find a balance in this kind of work.

        • says

          Thank you Ahmie – unfortunately we’re not the ones doing the research on SIDS. There are excellent researchers who do this. However, I also have learned in the short time since that parental apnea HAS been examined as a risk factor and not found to significantly contribute. However, what has not been examined is parental arousability which may be hereditary. Hopefully some researchers can look at this!

          • Ahmie says

            I strongly doubt that apnea has been able to be conclusively ruled out, it would require participation from parents who have suffered these losses having sleep studies done after their baby died. Sleep apnea is vastly underdiagnosed, a lot of people don’t realize that is why they are snoring. My husband’s family was unaware of it until I insisted that he have a sleep study done, and he wound up having surgery to remedy the problem (obstructive sleep apnea). To the best of my knowledge, the other family members I’ve heard having obvious apnea episodes when I’ve been around them while they were sleeping near me have not had sleep studies done. We didnt’ realize my husbands was as severe as it was before the night hooked up to machines told us he was stopping breathing at least once/minute, and some of those for prolonged times. He’s a VERY sound sleeper, I am a very light sleeper. THere are also different forms of sleep apnea and it could be that one is more of a risk for SIDS than the obstructive form. I believe one of the forms is a neurological one. If a family knows they have apnea in the family, a movement sensor under the baby’s mattress in a sidecar arrangement could be a lifesaver (as well as a really annoying device if they don’t remember to turn it off when picking the baby up!).

            But all this is just more of why those artificial baby milks advertised as helping babies “sleep more soundly” horrify me so much. Babies are worth losing sleep over.

          • says

            It is James McKenna who informed me that there was a ton of research in the 1970s looking at sleep apnea in this so I do trust his judgment that *parental* apnea is not a risk factor (that is the question here). Of course, as he mentioned, parental arousability may very well remain an issue, but as yet is unexplored.

          • Ahmie says

            Thanks for the source – I thought it might be him but wasn’t sure and haven’t had a chance to go digging yet. Could also be time for some follow-up study if it was that long ago. I’m very much a Dr. McKenna fangirl 😉 I like the way he asks questions and finds ways to test them. He’s a major academic inspiration to me and I’m glad I had the chance to tell him this in person a couple years ago. I will go read for myself how he tested the hypothesis.

          • says

            Sorry should have been clear – I’m not sure HE did the studies. He’s the one that told me about them when I mentioned the apnea question :)

          • Ahmie says

            ahh ok I’ll try to find them in a bit. Tell him the EEA mama in a mobility scooter says “hi” and now has four sons. I took my son who turns 3 tomorrow to the symposiums and was expecting my 4th when I went this past fall. He might not remember my name but I’m pretty sure the mental image is memorable enough 😉 He really is a hero of mine, his work gave me the confidence to mother my children the way I knew was right and the empowerment to go on to graduate school after a decade away from academia.

  4. Nicky says

    Thank you very much for this. I have not looked at the articles in full yet but plan to do some digging around the subject asap. One thing I would like to raise that has not been mentioned… SIDS increases between 2-4 months approx… this just happens to coincide with infant vaccines? Doesn’t vaccinations increase cortisol levels? There was a journal article a couple of years ago which compares the number of vaccines given in various countries and the SIDS rates. There was a correlation, when more vaccines were given SIDS rates increased. Until someone can actually include some info on whether vaccines were given at the usual age, whether they were delayed or whether they were not given at all, it would help as babies can have changed behaviour with vaccines even if no conclusive link to SIDS is found. Vaccines are a personal choice and I do not want to get into a debate on that,I just know that it seems to be avoided in all the studies done on SIDS, which is a shame. Thanks for the info above though. :-)

    • Ahmie says

      it is possible (and I am very much pro-individualized-medical-decisions/anti-blanket-medical-policy), but I do suspect that a likely bigger component is that this is also the age at which a lot of babies are switched to formula, particularly in the US where women don’t get paid maternity leave. Could be a combination of those two factors, too.

    • says

      I don’t doubt for some children there is an interaction. However, at a global level, it doesn’t seem to hold water. The study you’re thinking of is probably one on Japan, but the focus was on vaccine-related injury claims being reduced for SIDS, not rates of SIDS. Further, we have Sweden which has a comparable (though slightly less) schedule than the US and much lower rates of SIDS. Canada as well which has a nearly identical vaccine schedule but lower rates.

      • Nicky says

        No it wasn’t the Japan study, it is this one. It uses several Western countries and compares vaccines with SIDS rates.
        You mention Sweden – they use about 12 vaccines compared to USA with 26 – this is all before the child is 1 year, the USA have many more vaccines for after the 1st birthday. Sweden has lowest rates of SIDS (many more factors here such as home birth, health care and support etc) and USA at the opposite end. There is alot of inequality issues within this and it cannot be shown that the vaccines are the cause, but the authors do raise some interesting points.

        I’m not saying it would necessarily show anything, but it needs to be included. With more and more vaccines being included, and no-one looking at the bigger picture, the very least would be that it is given mention the next time an analysis is done on SIDS. Just my thoughts. :-)

  5. says

    Thank you for this fantastic resource. We have this conversation regularly in our boutique and find that the answer always come back to, “Do what is best for Baby and Mama”. Thanks again for this great resource!


  1. […] Vad jag förstår baserar socialstyrelsen detta på en studie som kom tidigare i år, en studie som blev hårt kritiserad från flera håll då författarna utelämnat viktig information och dragit slutsatser på lösa grunder. Läs gärna Unicefs kommentarer på studien och här en annan väl underbyggd kommentar. […]

  2. […] Men jag vet att andra länders myndigheter inte dragit samma slutsatser om samsovning grundat på samma studier. Svenska Socialstyrelsen har tidigare varit skeptiska till samsovning och den här studie som kom under 2013 verkar vara den som ligger bakom de hårdare råden. Studien som blev hårt kritiserad från flera håll. Läs gärna Unicefs kommentarer på studien och här en annan väl underbyggd kommentar. […]

  3. […] Men jag vet att andra länders myndigheter inte dragit samma slutsatser om samsovning grundat på samma studier. Svenska Socialstyrelsen har tidigare varit skeptiska till samsovning och den här studie som kom under 2013 verkar vara den som ligger bakom de hårdare råden. Studien som blev hårt kritiserad från flera håll. Läs gärna Unicefs kommentarer på studien och här en annan väl underbyggd kommentar. […]

  4. […] Det finns motstridig forskning om riskerna med plötslig spädbarnsdöd när föräldrarna samsover. En stor undersökning i Alaska fann att i 99 procent av dödsfallen med samsovande mödrar så fanns andra orsaker såsom alkoholintag. Denna undersökning fann alltså inga förhöjda risker orsakade av enbart samsovningen. Socialstyrelsens råd är baserade på en enda studie (Carpenter, som visserligen är en sammanslagning av data från fem mindre studier. Men flera av de ingående studierna har haft ofullständig information, bland annat om alkoholintag hos modern, och därför så har forskarna använt en metod för att gissa fram data (”imputation” på engelska). Jag är lite orolig för att detta kan ha lett till överdrivna slutsatser, då det inte framgår av artikeln hur de har hanterat den statistiska felmarginalen kopplat till gissandet och det framgår inte heller hur de tänkt kring det faktum att studierna ägt rum i olika länder, vilket borde göra det svårt att generalisera om alkoholvanor hos mödrar. Jag kan inte heller se att de har kontrollerat om någon förälder intagit sömntabletter (se också min bloggarkollega Evolutionary Parenting). […]

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