Is There Evidence That Light Drinking by Pregnant Women Harms Their Babies?

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Evidence of harm from light drinking during pregnancy

Check out this answer from Consensus:

The evidence suggests that light drinking during pregnancy may be associated with adverse outcomes such as SGA, preterm birth, neurodevelopmental impairments, and metabolic issues. Although the data is not conclusive, the precautionary principle supports abstention from alcohol during pregnancy to ensure the best possible outcomes for the child. Further research is needed to provide more definitive answers, but current guidelines recommend avoiding alcohol entirely during pregnancy.

The question of whether light drinking during pregnancy harms the developing fetus has been a topic of considerable debate. While heavy alcohol consumption is well-documented to cause severe developmental issues such as Fetal Alcohol Spectrum Disorders (FASD), the effects of light drinking are less clear. This article reviews the current evidence on the impact of light alcohol consumption during pregnancy on fetal and child health outcomes.

Evidence from Systematic Reviews and Meta-Analyses

Two comprehensive systematic reviews and meta-analyses have examined the effects of low-to-moderate alcohol consumption during pregnancy. Both studies found limited but concerning evidence suggesting that even light drinking could be associated with adverse outcomes.

  1. Low Alcohol Consumption and Pregnancy Outcomes: This review included 24 cohort and two quasi-experimental studies. It found that light drinking (up to 32g/week) was associated with a higher risk of small for gestational age (SGA) and preterm birth, although the evidence was not robust enough to make definitive conclusions. The authors recommended abstention as a precautionary measure due to the paucity of evidence.
  2. Effects of Low Alcohol Consumption on Pregnancy and Childhood Outcomes: This study similarly found that light drinking was associated with increased odds of SGA and preterm birth. The results were imprecisely estimated, but the authors suggested that guidelines should advise abstention due to the potential risks.

Neurodevelopmental and Metabolic Outcomes

Research has also explored the impact of light to moderate prenatal alcohol exposure (PAE) on neurodevelopmental and metabolic outcomes.

  1. Neurodevelopmental Impairments: Moderate alcohol exposure has been shown to impair neurodevelopment in both epidemiological studies and preclinical models. These impairments include cognitive and behavioral deficits, which support recommendations for complete abstention during pregnancy.
  2. Metabolic Consequences: A study on rats demonstrated that even moderate alcohol exposure during pregnancy could lead to insulin resistance in male offspring, suggesting potential long-term metabolic issues.

Clinical and Observational Studies

Several clinical and observational studies have provided additional insights into the potential risks of light drinking during pregnancy.

  1. Minor Anomalies and Umbilical Cord Contractility: A study found that light maternal ethanol consumption was associated with a higher frequency of minor anomalies in newborns and altered contractility of umbilical cord arteries, indicating potential developmental disruptions.
  2. Birth Weight and Preterm Delivery: Another study reported that light to moderate drinking was associated with decreased birth weight and increased risk of preterm delivery, particularly in women who also smoked during pregnancy.

Public Health Perspectives

Public health guidelines generally recommend abstention from alcohol during pregnancy due to the potential risks and the lack of a known safe level of alcohol consumption.

  1. Attitudes and Experiences: A qualitative study revealed that while most pregnant women and healthcare professionals believed abstention was safest, some women felt that the evidence against low-level drinking was insufficient. This highlights the need for clear and consistent guidelines.
  2. Policy Recommendations: Given the potential for even light drinking to cause harm, many health organizations advocate for complete abstention during pregnancy to avoid any risk to the developing fetus  .



Is there evidence that light drinking by pregnant women harms their babies?

Annika C Montag has answered Likely

An expert from University of California, San Diego in Pharmacology, Epidemiology

We don’t yet have the data to say definitively that light drinking by pregnant women harms their babies but it is likely. Quite likely.

This is not the answer we want but the one supported by our current understanding of relevant mechanisms (some of which comes from animal studies) and the preponderance of human studies. Why is this question so difficult to answer? How is it that two women with similar “light” levels of alcohol consumption can have such different outcomes? These questions are complicated by the many factors at play: the timing and pattern of “light” drinking, differences in absorption and distribution of alcohol, genetic differences (maternal and fetal), comorbidities, nutritional status, other environmental exposures, when during fetal development the exposure occurs, and more. Postnatal confounding factors, such as nurturing, challenging, enriched environments, affect neural development and may mitigate or serve to hide negative effects of prenatal alcohol exposure or, in the case of less optimal environments, exacerbate them.

Brain development occurs throughout the entire pregnancy rendering the brain exquisitely vulnerable to alcohol exposure no matter when it occurs. Neurobehavioral effects are far more common than physical effects. Unfortunately, mild to moderate neurobehavioral effects may be difficult to detect and assess, as well as difficult to attribute to a specific exposure. Even in situations where the diagnosis of disabilities caused by prenatal alcohol exposure (collectively called fetal alcohol spectrum disorders or FASD) can be made, children are often undiagnosed or misdiagnosed (Chasnoff et al., 2015).

A few things to consider:

  •       Alcohol is a teratogen: it disrupts the development of the embryo and fetus
  •       Alcohol consumed by a pregnant woman readily crosses the placenta to the fetus
  •       Alcohol concentration in the fetal compartment rapidly reaches maternal levels
  •       FASD is common: A recent national study estimated that as many as 1 in 10 first-graders in the United States may be affected (May et al., 2018)
  •       Greater consumption is associated with greater risk, so “light” drinking is less harmful than “heavy” drinking, but no threshold has been detected (Sawada Feldman et al., 2012) and no safe dose has been identified

While we need more studies to clarify the precise effects of “light” levels of alcohol consumption under different circumstances, we have a responsibility to empower women to make informed choices. The current recommendation to not consume alcohol during pregnancy is well founded.

Two more things – they don’t answer the question but I still want to include them:

  1.     In addition to being heartened by our current lack of definitive evidence of harm when it comes to light drinking, women who realize they may have consumed alcohol prior to pregnancy recognition (or beyond) will appreciate that specific micronutrients (Kable et al., 2015) during pregnancy and a stable, caring postnatal environment can ameliorate the effects of the exposure. In addition, should there be negative effects, early diagnosis and intervention are important protective factors that help both the affected child and the family thrive (Streissguth et al., 2004)
  2.     Stigmatizing women who consume alcohol in pregnancy is not helpful. No woman wants to hurt her child. Exposures may happen before a woman knows she is pregnant; approximately half of all pregnancies are unplanned. When a woman drinks throughout pregnancy, it may speak to the strength of her addiction or the reasons she is drinking in the first place. In addition, the uncertainties discussed above, the pervasive role of alcohol in our society, and zombie-like misinformation probably all contribute to the occurrence of exposures. We need to learn to provide meaningful support to all the women we love (our sisters, girlfriends, wives …) to enable happy, healthy pregnancies.

Chasnoff IJ, Wells AM, King L (2015) Misdiagnosis and missed diagnoses in foster and adopted children with prenatal alcohol exposure. Pediatrics 135:264-270.

Kable J, Coles C, Keen C, Uriu-Adams J, Jones K, Yevtushok L, Kulikovsky Y, Wertelecki W, Pedersen T, Chambers C (2015) The impact of micronutrient supplementation in alcohol-exposed pregnancies on information processing skills in Ukrainian infants. Alcohol 49:647-656.

May PA, Chambers CD, Kalberg WO, Zellner J, Feldman H, Buckley D, Kopald D, Hasken JM, Xu R, Honerkamp-Smith G (2018) Prevalence of fetal alcohol spectrum disorders in 4 US communities. JAMA 319:474-482.

Sawada Feldman H, Lyons Jones K, Lindsay S, Slymen D, Klonoff‐Cohen H, Kao K, Rao S, Chambers C (2012) Prenatal Alcohol Exposure Patterns and Alcohol‐Related Birth Defects and Growth Deficiencies: A Prospective Study. Alcoholism: Clinical and Experimental Research 36:670-676.

Streissguth AP, Bookstein FL, Barr HM, Sampson PD, O’MALLEY K, Young JK (2004) Risk factors for adverse life outcomes in fetal alcohol syndrome and fetal alcohol effects. Journal of Developmental & Behavioral Pediatrics 25:228-238.


Is there evidence that light drinking by pregnant women harms their babies?

Mary J O’Connor has answered Likely

An expert from University of California, Los Angeles in Psychology

Here is a recent paper titled “Drinking During Pregnancy and the Developing Brain: Is Any Amount Safe?” which documents the evidence so far concluding “there is no known safe level of alcohol consumption during pregnancy is critical for society at large”.

Summary of the research: Heavy prenatal alcohol exposure can have lifelong, disabling effects on brain and cognition. Unlike animal studies, research on light-to-moderate drinking in humans demonstrates less consistent impact. Discussions of negative research findings in popular media underestimate potential adverse outcomes and complicate decisions about risks versus benefits of light-to-moderate drinking during pregnancy.


Is there evidence that light drinking by pregnant women harms their babies?

Paul R Gard has answered Likely

An expert from University of Brighton in Pharmacology

The term foetal alcohol spectrum disorders (FASD) describes the range of adverse effects that are consequences of prenatal alcohol exposure in humans. These range from severe growth impairment, abnormalities of facial anatomy, impaired gut function and problems with mood and behaviour to less severe intellectual disabilities and problems with behaviour and learning.

The global prevalence of FASD has recently been estimated to be 7.7 per thousand, ranging from 0.1 per thousand in the Eastern Mediterranean region to 111.1 per thousand in South Africa. Estimates in the UK suggest that approximately 1% of children born have some impairment as a consequence of prenatal alcohol exposure. Despite current health education guidelines, evidence suggests that around 20% of British women continue to drink alcohol in some way during pregnancy. At least half of all pregnancies are unplanned and therefore it is common for women to continue drinking without being aware that they may be pregnant. The data also suggest that around four to five per cent of UK women continue to drink 3 – 14 units per week as pregnancy progresses. If 20% of UK women drink ‘some’ alcohol during pregnancy, and 4-5% continue to drink during pregnancy, but the prevalence of FASD is 1%, it is clear that not all babies exposed to alcohol before birth develop FASD, but it is not known why some pregnancies are affected and some not.

It is still not possible, however, to give any definitive advice as to how much alcohol may be safe, and at what stages of pregnancy alcohol consumption poses the greatest risk. Most of the early descriptions of the adverse effects of prenatal alcohol exposure were case studies of pregnant women with alcohol dependency who were drinking approximately one bottle of spirits per day throughout pregnancy. There are no clear conclusions from case studies of women who consumed low amounts of alcohol whilst pregnant. The advice that ‘no alcohol during pregnancy is the only safe option’ is therefore the only evidence-based advice. 

A recent review of data generated from animal models of FASD concludes that high, acute doses of ethanol during the first trimester (equivalent of binge drinking on two or more occasions) results in the characteristic facial changes of FASD, as does chronic lower dose ethanol exposure during the same period. The situation changes, however, later in pregnancy when lower dose, consistent, prenatal ethanol exposure is seen to produce anxiety and depression-like symptoms and deficits of learning and memory, without the facial changes.

The question of what constitutes a ‘high, acute dose’ or a ‘low, chronic dose’, however, remains unclear. It must be recognised that animals and humans ‘handle’ (distribute and metabolise) alcohol differently, and therefore doses in mice or rats cannot be compared directly. Our own research uses alcohol exposure pre-conception, throughout pregnancy and during suckling until weaning. We estimate that our pregnant mice are consuming the equivalent of 500ml (two large glasses) of wine per day and we know that peak blood alcohol concentrations reach about 80 mg/dL (the legal limit for driving in the UK), but fall to zero. Hence these animals are not ‘drunk’. The offspring have some mild degree of increased anxiety and impaired learning and memory, but no anatomical changes.    

There is therefore not a clear answer to the question “Is there evidence that light drinking by pregnant women harms their babies?” FASD does not occur in the absence of alcohol, and some women seem to drink heavily during pregnancy without harming their baby. Some women give birth to babies with FASD yet report having drunk only very small amounts of alcohol on one or two occasions during pregnancy. What we don’t know is what is it about the mothers or the babies that predisposes to, or protects against, consequences of even light drinking during pregnancy.


Is there evidence that light drinking by pregnant women harms their babies?

Omar  Abdul-Rahman M.D. has answered Likely

An expert from University of Nebraska Medical Center in Paediatrics, Genetics, Medicine

There is no known safe level of alcohol use during pregnancy. See this recent paper that continues to show this.


Is there evidence that light drinking by pregnant women harms their babies?

James Sanders has answered Unlikely

An expert from University of Lethbridge in Psychology

Human studies of alcohol use by pregnant women and its effect on the developing fetus are fraught with methodological challenges. These may include issues with sampling; confirmation, recall, and desirability biases; distinction between light and moderate/heavy drinking; and assessment of harm, among others. Results from across these studies, however, have consistently failed to provide evidence of harmful effects of light drinking.

This does not mean that there is a known safe threshold of alcohol consumption during pregnancy, and future research may well identify adverse effects of light drinking. Currently, however, there is not evidence (in answer to the question above).

It is reasonable to be prudent when informing policy on alcohol use during pregnancy. No alcohol during pregnancy is best.


Is there evidence that light drinking by pregnant women harms their babies?

Molly J Goodfellow has answered Likely

An expert from University of Maryland in Neuroscience, Psychology

Studies in animal models of gestational alcohol exposure have provided evidence that even low levels of alcohol exposure can alter fetal development. While the number of studies in humans on the effects of light to moderate drinking during pregnancy is relatively low, many of them do provide evidence that even small amounts of alcohol exposure during gestation can be harmful. Given that we do have definitive evidence that heavy drinking during pregnancy can be harmful for the fetus and that we do not have definitive evidence that light drinking during pregnancy is safe, pregnant women and those trying to conceive should seek to minimize the amount of alcohol that they consume as much as possible. Pregnant women who are concerned about their ability to abstain should consult with their doctor to develop a strategy that reduces potential harm.

For some human studies that provide evidence of fetal harm by low-to-moderate alcohol exposure, see:

  1.   “Our results suggested that low‐to‐moderate alcohol consumption during pregnancy may negatively influence a child’s development and behaviour in several ways.”

Sundelin-Wahlsten et al (2017). Higher alcohol consumption in early pregnancy or low-to-moderate drinking during pregnancy may affect children’s behavior and development at one year and six months. Acta Paediatrica, 106 (3): 446-453.

  1.   “This quasi‐experimental study suggests that moderate alcohol drinking in pregnancy contributes to increased risk for children’s early‐onset‐persistent conduct problems, but not childhood‐limited or adolescence‐onset conduct problems.”

Murray et al (2015). Moderate alcohol drinking in pregnancy increases risk for children’s persistent conduct problems: causal effects in a Mendelian randomization study. The Journal of Child Psychology and Psychiatry, 57 (5): 575-584.

this study pro-

vides evidence that moderate drinking is associated with fetal

growth and moderate drinking and binge drinking are related

to neonatal asphyxia.

  1.   “…this study provides evidence that moderate drinking is associated with fetal growth and moderate drinking and binge drinking are related to neonatal asphyxia.”

Meyer-Leu et al (2011). Association of moderate alcohol use and binge drinking during pregnancy with neonatal health. Alcoholism: Clinical and Experimental Research, 35 (9):1669-1677.

For some animal studies that provide evidence of fetal harm by low-to-moderate alcohol exposure, see:

  1.   “This study adds to the growing body of evidence that suggests that prenatal alcohol exposure, even at moderate levels, is associated with poorer offspring cognitive task acquisition and behavioral disturbances.”

Schneider et al (2001). Moderate alcohol during pregnancy: learning and behavior in adolescent rhesus monkeys. Alcoholism: Clinical and Experimental Research, 25 (9): 1383-1392.

  1.   “Although further research is required to understand fully the potential consequences of MPAE [moderate prenatal alcohol exposure], studies with animal models clearly indicate that MPAE can significantly affect brain development. Clinicians should take the findings of these studies into account when advising women about ethanol consumption during pregnancy and should also consider MPAE as a potential cause of neurobehavioral disorders identified during adulthood.”

Valenzuela et al (2012). Does moderate drinking harm the fetal brain? Insights from animal models. Trends in Neurosciences, 35 (5): 284-292.


Is there evidence that light drinking by pregnant women harms their babies?

Michael Charness M.D has answered Likely

An expert from Harvard University in Neurology, Addiction

Moderate levels of alcohol have been shown to disrupt the activity of a number of molecules that are critical for normal brain development. 

One such example, the L1 cell adhesion molecule, guides the migration of brain cells and the formation of connections between brain cells. Children with mutations in the L1 gene have developmental disabilities and brain malformations, and, importantly, the function of the L1 molecule is also disrupted by concentrations of alcohol that a woman would have in her blood after a single drink. These kinds of experiments support the view that women who are pregnant or trying to conceive would be safer to abstain from alcohol than to engage in even occasional light drinking.

Absence of proof is not proof of absence. The absence of evidence for developmental abnormalities in women who drink small amounts occasionally during pregnancy does not prove that light drinking is safe. Clinical studies do not have the power to detect small effects of alcohol on brain development, and even significant effects might be missed if the wrong test is used or if testing is conducted at the wrong developmental period. More practically, it is impossible to assure a mother who drinks lightly during pregnancy that her drinking did not result in a small drop in the IQ of her child. Light drinking is not essential to the health or well being of a pregnant woman, so why take a chance?

This expert answer was originally published here at the National Organization on Fetal Alcohol Syndrome.


Is there evidence that light drinking by pregnant women harms their babies?

Loubaba  Mamluk has answered Likely

An expert from Bristol University in Epidemiology

While heavy drinking is clearly harmful to the unborn baby, often leading to miscarriage, premature birth and foetal alcohol syndrome, the possible effects of light drinking have been less clear.

Women often ask about “safe” levels of drinking during pregnancy. The distinction between light drinking and abstinence is indeed the point of most tension and confusion for health professionals and pregnant women, in many countries around the world.

Our recent review of the evidence, published in BMJ Open, shows that this specific question is not being researched thoroughly enough. 

As there was some evidence, however, that even light drinking can be linked with babies being born small for their gestational age, our study confirms that advising women to abstain during pregnancy is indeed the safest option.

This evidence supports the new guidelines released by the UK’s Department of Health in January 2016. The guidelines advise women not to drink any alcohol when pregnant or trying to conceive. This was based on a “better safe than sorry” principle, and in light of our findings, it seems the sensible choice.

This is what we did in our review. As there can be no clinical trial research carried out on this topic, we systematically reviewed all the data from a wide range of high quality observational studies. These studies involved pregnant women, or women trying to conceive, who reported on their alcohol use before the baby was born. 

We compared light drinking to not drinking in pregnancy at all. Our definition of ‘light drinking’ was based on recommended maximum level given by the UK Department of Health’s previous guidance (the recent guideline came out while we were in midst of our research). This was one to two UK units, once or twice a week. Four units of alcohol – the maximum amount of alcohol per week – is equivalent to two pints of strong beer or two medium-sized glasses (175ml) of light white wine. Anything above that is considered moderate or heavy drinking, and wasn’t evaluated in our study.

Answer written in collaboration with Dr Luisa Zuccolo of Bristol University.


Is there evidence that light drinking by pregnant women harms their babies?

Adrian Esterman has answered Likely

An expert from University of South Australia in Epidemiology

At the moment, we do not have strong evidence that light drinking of alcohol during pregnancy is harmful to the foetus or child as it grows up. However, recent animal studies do show a potential for risk.

As such, it is wise for pregnant women to abstain from alcohol during pregnancy, until we have better evidence, and this is in fact the Australian National Health and Medical Research Council recommendation.

One major problem is that many women drink alcohol, perhaps heavily, before they know they are pregnant, by which time some damage might already be done. Perhaps the best policy is that if women are trying to get pregnant, they should avoid alcohol if possible, and certainly not undertake heavy drinking.


Is there evidence that light drinking by pregnant women harms their babies?

Shiva  Singh has answered Likely

An expert from University of Western Ontario in Genetics, Genomics, Neuroscience

To summarise: No alcohol dose is guaranteed to be 100% safe for the embryo/fetus and no time during pregnancy is 100% safe to drink.

Finding the cause and applying the insights toward prevention and treatment forms the ultimate goal of most disease research. This strategy has been successfully used to make diseases like Scurvy and Smallpox, a history. The impact of this research during the last few years has been nothing less than miraculous. More and more people are living longer with healthy and productive lives, well into the 80’s and 90’s. Discovery of the cause(s) of disease(s) however is a demanding, time consuming, and expensive exercise. Also, there is no guarantee for success. Yet, even the modest success in search for causes have the potential to change the outcome and perception. Early diagnosis of a number of cancers for example is now viewed as treatable with reasonable chance of recovery. Also, some heart diseases are being managed and treated with high rate of success. Given this record of success, the research on disease causations continues to increase and the results have begun to pay increasing dividend. Unfortunately, there are cases of diseases where even full understanding of the cause has not resulted in the prevention or treatment of some common and devastating diseases. One such disease is the fetal alcohol spectrum disorder (FASD).

FASD is caused by the exposure of developing fetus to alcohol via maternal drinking during pregnancy (Jones and Smith, 1973). It represents the biggest single cause of mental retardation and developmental disabilities among babies born in the Western World (Barry et al., 2009). In the U.S. more than 50,000 babies are born with FASD every year (May and Gossage, 2001) and the annual cost of treating FASD in Canada and U.S. exceeds $6 and $8 billions, respectively (Lupton et al., 2004; Popova et al., 2013). Although, the prevention of FASD is a high priority, the failure to prevent it is attributed to our alcohol culture. Most people drink for social and recreational purposes. Others are addicted to alcohol.

As it stands, there is no consensus on whether there is a “safe” limit for alcohol consumptions during pregnancy. Recent research involving animal (mice) models has shown that continuous exposure of low-to-moderate dose of alcohol during pregnancy impacts behavioral and cognitive outcomes of resulting pups (Kleiber et al., 2011) and even a single binge dose of alcohol at any time during pregnancy results in alterations in gene expression (Kleiber et al., 2012, 2013) and associated FASD related phenotypes. Furthermore, the molecular alterations may be initiated and maintained for life by alcohol’s effect on epigenetic features that includes DNA methylation (Laufer et al., 2013). The results on animal models argue that clinical features of FASD represent “tip of the iceberg.” They are also backed by results on humans. For example, exposure of human embryonic stem cells to low alcohol can alter gene expression leading to the abnormal development of prefrontal cortex (Krishnamoorthy et al., 2010). Also, fetal alcohol exposed school children show “a small but potentially important detrimental effect” on educational outcomes (Zuccolo et al., 2013) as well as generalized deficit of conceptualization (Quattlebaum and O’Connor, 2013).

We feel that such results deserve due consideration given that Royal College of Obstetrics and Gynecologists (Royal College of Obstetrician and Gynaecology, 2006) states that, “there is no evidence of harm from low levels of alcohol consumption, defined as no more than one or two units of alcohol once or twice a week.” Also, “there is considerable doubt as to whether infrequent and low level of alcohol consumption during pregnancy convey any long-term harm”—in other words they suggest a safe amount of alcohol consumption in pregnancy. Unfortunately, this limit has not been defined and may vary from individual to individual. Individual women process alcohol differently. Also, the age of the mother, the timing and regularity of the alcohol ingestion, and whether the mother has eaten any food while drinking may be important. We argue that there is no logistic evidence to define this limit. What is needed is to undertake thorough studies on neurodevelopment and assess the significance of such factors as maternal and fetal genotype, stress during pregnancy and childbirth, prenatal drinking patterns (mild, medium, heavy), post-natal environment, and socioeconomic status, as most of these may contribute to the manifestation of the effect of prenatal alcohol on the newborn. We note that some of these studies will be problematic if not impossible on humans. The rational question is “does no evidence of harm from low levels of alcohol consumption means 100% exclusion of the possibility of any harm to the fetus?” To the best of our understanding the answer is “no.”

The issue is particularly problematic as there is a rise in heavy drinking by young people, particularly women. Often, it is framed, as freedom of choice or “a single drink will not harm.” Not surprisingly, 1 in 8 adult women and 1 in 5 high school girls binge drink (CDC, 2013) and there is ample evidence from animal experiments, which argue for a life-long effect of even a single exposure of alcohol during pregnancy. The developing brain is a sequential, multistage, closely orchestrated, and highly sensitive to stresses. Also, any aberration could lead to life-long abnormality. For now, it is prudent to prevent a brain disorder than to attempt to ameliorate or cure it. Preventing a single case of FASD will save the society $1 million. More importantly it will save a productive life. The business as usual model is not helpful. It continues to result in births with alcohol effects. Any harm caused by prenatal alcohol is currently not reversible. It will affect the child for life.

With the current knowledge of what causes FASD it is prudent to stay on the safe side and avoid any drinking during and around the pregnancy. FASD is an alcohol problem. It is possible to prevent this calamity by avoiding alcohol during pregnancy and the time is now! FASD is a preventable disease—by not drinking during pregnancy. On the other hand, finding “cure” will be much more challenging, costly and time taking. It is critical to undertake active measures to reduce the occurrence of this disorder by a message of “no alcohol dose is guaranteed to be 100% safe for the embryo/fetus.” Also, “no time during pregnancy is 100% safe to drink.” Any adult has the right to drink if they so wish. Also, every child has the right to be born healthy!

This article was originally published in Frontiers in Genetics


Is there evidence that light drinking by pregnant women harms their babies?

Jennie Connor has answered Likely

An expert from University of Otago in Epidemiology, Medicine

The reason for lack of conclusive evidence about this question is the difficulty in studying it. However there is certainly no good evidence of a definable amount of alcohol or fetal age where drinking alcohol is completely safe. Extrapolating from other known neurotoxic effects of alcohol you would expect effects of light drinking on the fetus to be less frequent and less severe, on average, than the effects of larger doses of alcohol, which is one reason it is hard to study. Also, low volume drinking is difficult to measure by self-report and particularly sensitive in this context. Ability to measure cognitive potential and other sequelae in infants is also challenging. None of that rules out cognitive impairment in some individuals from light drinking that will be life-changing for the children and their families. It is unlikely that it will ever be possible to show a safe level or period, but it may eventually be possible to show definitive harm.


Is there evidence that light drinking by pregnant women harms their babies?

Alessandro Ieraci has answered Likely

An expert from University of Milan in Neuroscience

Preclinical and clinical studies suggest that even low levels of alcohol consumption during pregnancy may impact brain development and that these effects persist into young adulthood.


Is there evidence that light drinking by pregnant women harms their babies?

Susan J Astley has answered Likely

An expert from University of Washington in Epidemiology, Global Health

There is compelling evidence that light drinking by pregnant women places their babies at risk. As documented in a published letter to the editor to the British Journal of Gynaecology in 2012 (Astley SJ, Grant T. Another perspective on ‘The effect of different drinking patterns in early to mid pregnancy on the child’s intelligence, attention, and executive function’. Letter to the Editor, BJOG 2012;1672, DOI: 10.1111/1471-0528.12008):

It has been suggested in a series of papers published on 20 June 2012 in BJOG that low and moderate weekly alcohol consumption in early pregnancy is not associated with adverse neuropsychological effects in children aged 5 years. The authors of the papers state that it remains the most conservative advice for women to abstain from alcohol during pregnancy; however, small amounts may not present a serious concern.

The researchers studied 870 preschool children whose mothers reported drinking during pregnancy and compared them with 758 preschool children whose mothers reported not drinking during pregnancy. They measured the children’s IQ and attention levels at the age of 5 years. Children exposed prenatally to 1–8 drinks per week had the same IQ and attention levels as children with no exposure to alcohol.

We contend that the reason the children in this study did not appear to be harmed by the alcohol is because the children were too young to measure the full impact alcohol may have had on their brains. At 5 years of age, the brain is still developing. A 5-year-old’s brain is not developed sufficiently to perform complex tasks, such as remembering and following multiple instructions, writing a report, communicating abstract ideas effectively or exercising good judgment. Over 30 years of research on fetal alcohol syndrome (FAS) confirms that alcohol has its greatest impact on complex brain functions.6 This is why children exposed to and damaged by prenatal alcohol exposure do deceptively well in their preschool years. The full impact of their alcohol exposure will not be evident until their adolescent years.

Please consider the following statistics based on 2,600 children who received a diagnostic evaluation for FAS in the Washington State FAS Diagnostic & Prevention Network clinics over the past 18 years.

  • One of every seven children diagnosed with FAS (the most severe outcome caused by prenatal alcohol exposure) had a reported exposure of 1–8 drinks per week. (The Danish studies did not conduct FAS diagnostic evaluations on the children.)
  • One-half of the children with FAS had developmental scores in the normal range as preschoolers. However, all had severe brain dysfunction confirmed by the age of 10 years. (The Danish studies only assessed preschoolers.)
  • Only 10% of the children with FAS had attention problems by the age of 5 years; 60% had attention problems by the age of 10 years. (The Danish studies only assessed attention at the age of 5 years.)
  • Only 30% of the children with FAS had an IQ below normal. However, 100% had severe dysfunction in other areas, such as language, memory and activity level. (The Danish studies did not assess these areas.)

Although the science may be complicated and studies sometimes yield conflicting messages, the public health message is simple: to have the healthiest baby possible, women should not drink alcohol when trying to conceive and during pregnancy. When a pregnant woman drinks, her child is at risk. If she drinks heavily, her child is at higher risk.


Is there evidence that light drinking by pregnant women harms their babies?

Dimitrios E Kouzoukas has answered Likely

An expert from Loyola University Chicago in Neurobiology, Pharmacology, Molecular Biology, Neuroscience

Alcohol should be avoided during pregnancy. Alcohol is a teratogen and excessive alcohol consumption by pregnant women is known to produce a distinct pattern of birth defects and mental retardation.  However, considerable variability of symptoms exists in babies delivered from women reporting having drank identical quantities of alcohol. This suggests the amount and pattern of alcohol consumption are key risk factors.  Supporting the clinical data are many animal studies identifying vulnerable brain regions and critical periods of neurodevelopment that are most affected by alcohol exposure.


Is there evidence that light drinking by pregnant women harms their babies?

Hayley Passmore has answered Likely

An expert from Telethon Kids Institute  in Psychology, Health, Criminology

We don’t know how much alcohol, if any, is safe to drink during pregnancy. For women who are pregnant or planning a pregnancy, not drinking is the safest option.

Several articles have been published which suggest that low levels of prenatal alcohol use can affect fetal development. An example can be found here:

For more information on alcohol use during pregnancy, planning a pregnancy or breastfeeding, please visit these websites:


Is there evidence that light drinking by pregnant women harms their babies?

Mariko Saito has answered Likely

An expert from The Nathan S. Kline Institute for Psychiatric Research in Neurochemistry, Developmental Biology

There may be no firm evidence showing that light drinking by pregnant woman harms their babies. However, at the same time, there is no known safe levels of alcohol which pregnant woman can consume without any adverse effects on their babies. Preclinical studies using animal models do indicate that light drinking harms offspring, and the severity of the adverse effects is much influenced by genetic and environmental factors. These preclinical studies suggest that there is always the possibility that light drinking by pregnant woman harms their babies.  


Is there evidence that light drinking by pregnant women harms their babies?

Emma L Louth has answered Likely

An expert from Aarhus University in Neuroscience

The short answer to this question is that researchers recommend that there is no safe amount of alcohol to drink during pregnancy.

I would recommend this article Drinking during pregnancy and the developing brain: is any amount safe? for a short explanation on why researchers would still say there is no safe amount to drink, even when there are some large scale studies that find no link between light drinking and harm to a developing fetus.


Is there evidence that light drinking by pregnant women harms their babies?

Mathew Parackal has answered Likely

An expert from University of Otago in Social Sciences

Research has not established a safe amount of alcohol during pregnancy. You may ask why researchers have not established as yet? One reason is the ethical challenge of such an investigation. What we know for sure is that alcohol freely transfers from the mother to the baby’s bloodstream via the placenta. As the mother’s liver breaks down alcohol (Burd et al 2012), sometimes the blood alcohol concentration of the baby can be higher than that of the mother, until all the alcohol is removed.

An alcohol-exposed pregnancy causes many birth defects in the baby, collectively called Fetal Alcohol Syndrome Disorder (FASD). FASD is a lifelong burden for the baby. For the mother and family, life is no longer the same from the day their baby is diagnosed with FASD.

The question of how much is safe is an important one. The safest answer is “NONE” as many factors influence the outcome of drinking in pregnancy and hence it is difficult to pinpoint a “safe” amount. Equally important is the style of drinking. Our research shows that regular drinking and binge drinking are significant risk factors for an alcohol-exposed pregnancy (Parackal et al 2013). With over 40% of pregnancy being unplanned (Singh et al 2010), many are unknowingly drinking into the early stage of their pregnancy (Parackal et al 2013). Many women tend to drink, sometimes heavily on the weekend or in a party, until pregnancy is recognised. The damage, unfortunately, is inflicted by then. 


Burd, L., Blair, J., & Dropps, K. (2012). Prenatal alcohol exposure, blood alcohol concentrations and alcohol elimination rates for the mother, fetus and newborn. Journal of Perinatology, 32(9), 652.

Parackal, S. M., Parackal, M. K., & Harraway, J. A. (2013). Prevalence and correlates of drinking in early pregnancy among women who stopped drinking on pregnancy recognition. Maternal and Child Health Journal, 17(3), 520-529.

Singh, S., Sedgh, G., & Hussain, R. (2010). Unintended pregnancy: worldwide levels, trends, and outcomes. Studies in Family Planning, 41(4), 241-250.


Is there evidence that light drinking by pregnant women harms their babies?

Clark W Bird has answered Likely

An expert from University of New Mexico in Neuroscience

There are conflicting studies in human subpopulations regarding the effects of light/moderate drinking during pregnancy, with some studies demonstrating that light maternal drinking has negative developmental outcomes, while others find no consequences of alcohol exposure. The problem with these studies is that they are observational in nature, and not subject to strict experimental controls (for obvious reasons- performing a designed experiment on humans in which 1/2 the mothers drink and the other 1/2 do not is not exactly ethical). To draw conclusions about the risk of gestational exposure to alcohol, we must look at the results of experiments that use animal models.

The majority of experiments that model exposure to moderate ethanol levels during development in rodent models have shown neurological and behavioral deficiencies result. These can be deficiencies in social behaviors, motor coordination, learning and memory, fear responses, etc. We can conclude from these experiments that exposure to ethanol during gestation is harmful to the developing animal.

Many studies in humans haven’t been able to demonstrate an overt deficiency in kids who were exposed to alcohol in the womb and those who weren’t. It is likely, however, that some of these deficiencies are too subtle to be measurable using the tests we have available. If developmental ethanol causes a deficiency of a few IQ points, you wouldn’t be able to measure this in any meaningful way. If you want your child to have every possible advantage in life, including those extra few IQ points, it would be advisable to abstain from consuming alcohol while pregnant.

For a review of animal studies involving moderate gestational ethanol exposure, please see Valenzuela CF, Morton RA, Diaz MR, Topper L. 2012. Does moderate drinking harm the fetal brain? Insights from animal models. Trends in Neurosciences 35 (5): 284-292.


Is there evidence that light drinking by pregnant women harms their babies?

John C Thorne has answered Likely

An expert from University of Washington in Linguistics

The ability to do definitive causal studies about prenatal alcohol exposure is limited due to ethical considerations, so the bulk of the evidence for the risk of light drinking comes from indirect sources – most importantly an extensive literature using animal models. Newer techniques such as “Mendelian Randomization” are helping to support the case as well (see for one example).

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