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Drinking guidelines say women should avoid alcohol altogether when pregnant, but what's the evidence low-level drinking causes harm?
It's been five years since Australian drinking guidelines changed to advise woman to avoid alcohol altogether when pregnant or trying for a baby. Yet a significant number of women continue to drink during pregnancy and confusion about this issue remains high.
Studies show between 50 and 80 per cent of Australian women consume at least some alcohol during pregnancy. And it's not just women who are ignoring the guidelines. There's even anecdotal evidence some obstetricians tell their patients the occasional drink is fine, says one of Australia's key alcohol and pregnancy researchers, Dr Colleen O'Leary.
This week, the debate continued with a letter published in the Medical Journal of Australia criticising the guidelines for causing unwarranted anxiety among women who had drunk alcohol at low levels. Some such women, fearing they had harmed their unborn baby, might even consider an unnecessary termination, the letter by an obstetric drug information consultant said.
Confusion may be partly responsible for why so many women continue to drink despite being clearly advised not to. The recommendations in the alcohol guidelines has shifted from abstinence in 1992 to saying a little was OK no more than two standard drinks a day and less than seven a week in 2001, and back to abstinence in 2009.
No-one disputes alcohol increases the risk of harm to an unborn baby (see Fetal Alcohol Spectrum Disorders (FASDs) and Fetal Alcohol Syndrome (FAS) box), and this risk is highest when the mother drinks a large amount of alcohol very often. But at the lower end of the drinking spectrum, the risks are less clear.
So what's the evidence low-level drinking causes harm?
O'Leary, adjunct research fellow at Perth's Telethon Kids Institute for Child Health Research, recently reviewed all the evidence relating to low to moderate alcohol exposure during pregnancy.
She found no strong research showing harm from low-level drinking, which she defined as one to two standard drinks per occasion but less than seven standard drinks a week.
Her finding echoes that of a similar review from 2007, which found no convincing evidence of increased risk of stillbirth, growth restriction in the fetus, or prematurity from low level alcohol consumption. But weaknesses in the studies reviewed meant the authors couldn't conclude that drinking at these levels is safe, just that the evidence is inconclusive.
Despite the lack of clear evidence of harm from low-level drinking, O'Leary nonetheless believes the current guidelines are right in recommending pregnant women stay away from the bottle completely.
This is because it has been shown that a relatively small increase in the amount of alcohol a woman drinks can have a significant effect on her unborn baby.
"There isn't strong evidence one glass of alcohol is going to cause harm but there is good evidence that three to four standard drinks that's just [about] two [average] glasses of wine [no more than] once or twice a week might," O'Leary says.
This "moderate" level drinking increases the risk of the child developing behavioural problems including aggression, depression and anxiety between the ages of two and 15, she says, adding there's also good evidence for an increased risk of preterm birth.
With "such a small margin" before there is increased risk to the fetus, it would be "morally and ethically unacceptable" for guidelines to condone any drinking during pregnancy, she says.
Scientists may never be able to conclusively prove that low level drinking in pregnancy is safe. And even if they could, "the best advice is not to drink at all because it's too easy to drink more than you think" and slip into the range that does increase the risk of harm.
Drinks such as wine often contain a higher percentage of alcohol than women realise, making it easy to overdo things. "And people top up your glass without you noticing. There's all those sorts of factors involved.
"What you want to be doing during pregnancy is reducing the number of risks to your baby's development. The guidelines are there to set the standard for the best care. I think women should follow them."
But clearly, not all women do choose to follow this advice. And perhaps that's not surprising. After all, about 90 per cent of the population drinks and this widespread tolerance of alcohol in society, combined with our limited knowledge of its risks during pregnancy means it's easy for the potential harm to be overlooked.
"The difficulties people in our society face in not drinking are tough even when they're pregnant," says Michael Thorn, chief executive for the Foundation for Alcohol Research and Education (FARE). "Research suggests people are even reluctant to say 'I'm not going to have a drink because I'm pregnant'."
O'Leary likens the situation to the early days when tobacco's ill-health effects first came to light.
"Smoking was very prevalent in the community, including among health professionals," she says. "There was a lot of denial and it's taken a long time for people to support restrictions on smoking in our society. I think the same idea is there for alcohol as well.
"The ultimate goal is to redefine 'normal' alcohol drinking patterns so that harmful drinking and drinking during pregnancy become socially unacceptable."
And what about women who drink before they know they're pregnant or those who have a drinking habit they cannot break?
"Over-interpretation of risk leading to comments such as 'even one drink can harm your baby', will lead to more harm than good", she believes, with potential for women to consider terminating a pregnancy or hiding a drinking habit and avoiding getting help.
For this reason, she opposes laws being considered in the Northern Territory that would prosecute or restrain pregnant women if they drink dangerously.
"All that [such laws] will do in my opinion is push women underground who want to continue drinking. Some cannot stop and we need to recognise that. They will be very reluctant to approach services for fear of losing the child or some sort or punitive measures."
Instead she says women unable or unwilling to abstain should be offered supportive antenatal services, advice about nutrition and treatment as appropriate.
Low-level alcohol exposure appears to be low risk and not all fetuses, even when exposed to higher levels will be harmed.
"But fetal development is a complex process and avoiding known risk factors is the best choice to make."
Fetal Alcohol Spectrum Disorders (FASDs) are a group of conditions that can occur in a person whose mother drank alcohol during pregnancy. These effects can include physical problems, as well as issues with behaviour and learning. (Note that FASD itself is not intended to be a diagnosis, although doctors do diagnose the individual conditions within it.)
All children with FASD have abnormalities of brain structure and/or function and may also have:
The features in children exposed to alcohol during pregnancy vary and not all babies exposed even at a high level will be affected at all. However there is no known amount of alcohol that is safe to drink while pregnant.
FASDs include Fetal Alcohol syndrome (FAS) which represents the severe end of the FASD spectrum, according to the US Centers For Disease Control and Prevention (CDC).
There are no reliable figures for the prevalence of FASD or FAS in Australia, O'Leary says.
"Determining the prevalence of FASD when there is no objective test for it, and the FAS facial features don't need to be present, is very difficult."
It is known that many children with FAS do not receive a diagnosis for reasons including doctors not wanting to stigmatise a child or doctors not knowing the diagnostic criteria, O'Leary says. There is also anecdotal evidence many of the cases diagnosed are not reported to central registries.