Alcohol consumption by pregnant women continues to be controversial (O’Brien 2007, Nathanson et al. 2007). Alcohol readily crosses from the maternal blood stream via the placental barrier into the foetus’s blood stream where it circulates until it is broken down or metabolised by the foetus’s, albeit undeveloped, liver. Alcohol also enters breast milk by passive diffusion within 30 to 60 minutes of ingestion reflecting the maternal blood alcohol concentration (Giglia and Binns 2006).
There has been a plethora of information and literature lately on the effects of maternal alcohol consumption on the developing embryo, foetus and child. Alcohol can affect or influence neurological development as well as overall gestational growth and viability. The most severe adverse effect is foetal alcohol syndrome (FAS), which was independently described by Lemoine et al. in 1968 and by Jones et al. in 1973. The evidence linking chronic or intermittent heavy maternal alcohol consumption with harm to, and adverse effects on, the foetus is convincing, but it is less convincing and less certain for risk of harm for low to moderate maternal alcohol consumption (O’Leary 2004; Abel 2009). The majority of the literature still does not support the ‘no threshold theory’, that any amount of alcohol will have a harmful effect on the foetus, but a threshold has not been determined as yet.
Hence, exposure of the foetus to alcohol is now considered to be a preventable harm and, therefore, an issue for public health concern and policy. This consideration is behind the changing Australian and international government guidelines for alcohol consumption during pregnancy and while breast feeding. Governments are beginning to advise that all women of child-bearing age should be aware, before they consider pregnancy, of the potential risks of harm to the developing embryo, foetus and child, so that they can make informed decisions about their alcohol consumption during pregnancy and while breast feeding. Indeed, 12 countries have a guideline for alcohol consumption during pregnancy. Ten of these 12 are unanimous in stating that pregnant women or those planning pregnancy should abstain from alcohol. Abstinence is also recommended during breast feeding.
The new National Health and Medical Research Council’s Australian Guidelines to reduce health risks from drinking alcohol (2009) state that: “Maternal alcohol consumption can harm the developing foetus or breast feeding baby. For women who are pregnant or planning a pregnancy, not drinking is the safest option. For women who are breast feeding, not drinking is the safest option.”
This is a revised version of the 2001 Guidelines which stated that: “women who are pregnant or might soon become pregnant may consider not drinking at all; most importantly, should never become intoxicated.” The 2001 Guidelines also provided guidance to women who chose to continue drinking alcohol during pregnancy and when breast feeding. Indeed, they stated that: “if they choose to drink, over a week, they should have less than 7 standard drinks, AND, on any one day, no more than 2 standard drinks spread over at least two hours.” The guidelines advised that the risk is highest in the earlier stages of pregnancy, including the time from conception to the first missed period. The guidelines also advised that alcohol may adversely affect lactation, infant behaviour such as feeding, and the development of movement involving both mental and muscular activity (psychomotor) in the breast fed baby. As Australian and international guidelines recommend breast feeding children for the first six months, advice was provided for women who choose to drink in this period.
The UK guidelines of 2007 also recommend abstinence during pregnancy and advise against intoxication, but importantly also recommend that women who do choose to consume alcohol before and during pregnancy, should consume no more than 8-16g of alcohol once or twice a week. This is a revised version of the 1995 UK Sensible Drinking guidelines which recommended that pregnant women or those planning pregnancy should reduce their alcohol consumption to no more than 816 grams of alcohol per week. This recommendation was based on a review and report by the Department of Health’s Expert Committee on Toxicology (1995) that concluded that consumption of 16g of alcohol per day and above was associated with reduced birth-weight, but there was no convincing evidence that 8-16g of alcohol per week had any adverse effects on the developing foetus. A subsequent analysis of collected data on approximately 20,000 exposed foetuses, determined there was no evidence that moderate consumption, as distinct from light consumption, increased the risk of foetal abnormalities; where moderate consumption was defined as greater than two standard drinks of alcohol per week but less than two standard drinks per day in the first trimester (Polygenis et al. 1998).
The most severe adverse effect from chronic or intermittent heavy alcohol consumption by pregnant women is FAS. It is characterised by three diagnostic criteria: reduced growth, craniofacial and neurological abnormalities, and certain cardiac, central nervous system, limb and urogenital malformations. Primarily under consideration has been the amount and frequency of alcohol consumed by the mother that causes FAS. A review of the literature, both recent and past, reveals that:
FAS is only observed in babies born to women who excessively consume alcohol habitually and continually during pregnancy, approximately 50 to 60 g alcohol per day (Elliott et al. 2008), irrespective of ethnicity. In particular, binge-like drinking patterns, in which the foetus is exposed to high blood alcohol concentrations over relatively short periods of time, are particularly harmful, even if the overall amount of alcohol consumed is less than that of more continuous drinking patterns (Maier and West 2001).
The diagnosis of FAS (and that of foetal alcohol spectrum disorder) is confounded by other factors common to these women, such as the nutritional status of the mother, her ingestion of drugs including caffeine and nicotine as well as illicit drugs, her age, and her educational, ethnicity, genetic, marital, number of pregnancies (parity) and socio-economic status (Aase 1981, Sokol et al. 1986, Michaelis and Michaelis 1994, Abel and Hannigan 1995, Jacobson et al. 1996, Mattson et al. 2002, Guerrini et al. 2007, Elliott et al. 2008).
FAS has not been observed to occur in babies born to women who consume low amounts of alcohol during pregnancy, approximately 10 g alcohol per day (Henderson et al. 2007).
The critical period of exposure to alcohol is the first trimester.
The incidence of FAS is extremely small. In Australia, the incidence of FAS is approximately 0.014-0.02/1,000 live births and the incidence of low birth weight is 4/1,000 live births. These statistics have remained relatively stable over the past decade, which reflects the size of the readily identifiable ‘at risk’ groups. In the USA, the incidence of FAS is 0.5-2.0/1,000 live births (CDC 2009), which has also remained relatively stable over the last two decades (CDC 2009). These data suggest that the incidence of FAS is substantially lower in Australia than in the USA as well as in Finland, France, Italy and Sweden (Sampson et al. 1997), which may reflect different alcohol consumption patterns, diet and lifestyle, which could increase/decrease confounding factors .
The ‘at risk’ group is relatively small such that alcohol consumption levels before pregnancy are a strong predictor of alcohol use during pregnancy (Floyd et al. 1999, May et al. 2004). In Australia, only 1.0-4.3% of the 48-58% of women who consume alcohol while pregnant, consume heavily and continually, that is, consume five or more standard drinks on a typical occasion (Colvin et al. 2007, Giglia and Binns 2007). The proportion of women consuming one to two drinks on a typical occasion does not appear to change significantly during pregnancy, but the number of occasions decline. The majority of the women consuming alcohol while pregnant and breast feeding consume infrequently and only up to two standard drinks per week (Giglia and Binns 2007, Wallace et al. 2007). In the USA, the percentages of any alcohol use and binge drinking among pregnant and non-pregnant women of childbearing age has not changed over the past two decades (CDC 2009). The average annual percentage of any alcohol use among US pregnant women was 12.2%, of binge drinking among pregnant women was 1.9%, of any alcohol use among non-pregnant women was 53.7%, and of binge drinking among non-pregnant women was 12.1%.
The incidence of FAS is higher, however, in children born to indigenous groups. For example, the incidence of FAS in indigenous Australians is approximately 2.76/1,000 live births (Bower et al. 2000, Harris and Bucens 2003, Elliott and Bower 2004, Elliot et al. 2006). This is consistent with data from other countries for indigenous groups (May et al. 1983, Burd and Moffatt 1994, Stratton et al. 1996, Sampson et al. 1997, Chambers et al. 2005). These indigenous ‘at risk’ groups are minority groups, for example, indigenous Australians comprise 2.2% of the total population of their country, African Americans 12.8%, Native Americans and Alaskans 1%, Canadian Aborigines 3.3%, indigenous New Zealanders 15.7% and Native Taiwanese 2%. The higher rates of FAS in these minority groups reflect the greater presence of risk factors, such as low socio-economic status, poor nutrition, illicit drug use, the binge pattern of drinking and the greater amounts of alcohol being consumed by those who drink.
The incidence of FAS is also higher in children born into lower-socio-economic status groups. The higher incidences of FAS observed in South Africa, South America, Italy and other countries (Abel 1995, O’Connor and Whaley 2003, Chambers et al. 2005, May et al. 2006, 2007) come from the poorest groups in those countries. This may reflect poor nutrition and/or general health and, therefore, reduced resiliency to the effects of alcohol, or a combination of these and other factors.
Therefore, it has been clearly demonstrated in the literature that there are readily identifiable ‘at risk’ groups in the population, that behave significantly differently to the ‘not at risk’ groups, whose harmful amount and pattern of alcohol consumption is consistent and continued during pregnancy.
The relationship between alcohol consumption and other pregnancy outcomes apart from FAS also appears controversial and unclear. These outcomes are often referred to as foetal alcohol spectrum disorder (FASD). They used to be referred to in the literature as foetal alcohol effects, although there was considerable concern then that the term was being indiscriminately applied to children with a range of abnormalities and/or problems, both behavioural and growth, where it is purported that the mother has consumed alcohol during pregnancy (Little and Wendt 1991, Aase 1994, Aase et al. 1995, Abel and Hannigan 1995). Experimental studies have since documented the vulnerability of the developing central nervous system to alcohol (Guerri 1998, 2002). FASD is not in itself a clinical diagnosis but describes a full range or spectrum of disabilities that may result from exposure of the foetus to alcohol in pregnancy such as growth deficiencies, birth defects and neuro-developmental problems (Abel 1998, Sokol et al. 2003).
From the existing evidence, it is difficult to determine whether there is any adverse effect on pregnancy outcomes associated with low to moderate maternal alcohol consumption. For every paper that claims that any alcohol negatively influences a birth outcome, another paper refutes it. For example, Kesmodel et al. (2001) observed an increased risk of pre-term delivery with consumption of five or more alcoholic drinks per week at 16 weeks gestation and with consumption of more than one to two drinks per week at 30 weeks gestation but Albertsen et al. (2004) did not with four drinks per week over the gestation period. An increased risk of pre-term birth was also not observed by Parazzini et al. 2003, however, until more than three drinks on average per day were consumed.
Similarly, concerning low birth weight, while Covington et al. (2002) observed that more than 14 alcoholic drinks/week decreased birth weight and length, and lower weight at age seven years, O’Callaghan et al. (2003) did not observe this. Furthermore, Mariscal et al. (2005) observed that alcohol consumption of less than 6 g/day, actually decreased the risk for low birth weight but the risk was increased when more than 12 g/day of alcohol was consumed. The risk was decreased again when the 12 g/day was confined to weekends for non-cigarette smoking women. This also shows the confounding aspect of cigarette smoking and the importance of influence of patterns of alcohol consumption.
Concerning spontaneous abortion: Kesmodel et al. (2002) observed an increased risk of spontaneous abortion when five or more alcoholic drinks/week were consumed in the first trimester. This was corroborated by Henriksen et al. (2004), but at 10 or more alcoholic drinks/week. Neither result was observed, however, by Maconochie et al. (2007).
Concerning, how the brain affects emotion, behaviour, and learning (neurobehaviour) as well as perception, learning and reasoning (cognition), O’Callaghan et al. (2007) did not observe any adverse attention, learning or cognition outcomes when less than one alcoholic drink/day was consumed during pregnancy, but drinking more than this in late pregnancy and indeed binge drinking, was associated with an increased risk of overall learning difficulties. D’Onofrio et al. (2007) observed, however, that multiple drug use during pregnancy was a better indicator of behavioural and learning difficulties in children.
In conclusion, the tragedy of a child with FAS cannot be underestimated. While there is convincing evidence linking chronic or intermittent heavy alcohol consumption with harms, including adverse pregnancy outcomes and FASD, there remains uncertainty about the potential for harm to the foetus from low to moderate maternal alcohol consumption. A recent review by Hendersen et al. (2007) on the effects of low to moderate pre-natal alcohol consumption (up to 83g /week or eight standard drinks) on foetal and early childhood development concluded that there was no convincing evidence of adverse effects. However, methodological weaknesses in the reviewed research precluded the paper from concluding that alcohol consumption at any level is safe during pregnancy (Henderson et al. 2007). The UK National Institute of Clinical Excellence, however, still states that pregnant women can safely consume up to one and a half standard drinks per day after the first trimester. What can be stated with certainty is that the risk is higher with heavy maternal alcohol consumption, including binge drinking, it appears to be low with low to moderate maternal alcohol consumption, and it is currently impossible to determine how maternal and foetal factors will alter risk in the individual.
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Reprinted with kind permission for the Australian New Zealand Grapegrower and Winemaker.