Nurses should advise pregnant women to avoid all alcohol despite ‘surprisingly limited’ evidence of potential risks from occasional consumption, researchers have said.
A review of the pooled data available on the potentially harmful effects of occasional drinking in pregnancy, published today (11 September), concluded that expectant mothers should avoid all alcohol ‘just in case’.
The analysis showed that drinking, on average, up to four units a week while pregnant was associated with an 8% higher risk of having a small for gestational age (SGA) baby, compared with drinking no alcohol at all.
There was also some evidence of a heightened risk of premature birth, but estimates for preterm birth were ‘also compatible with no association’, the researchers found.
‘Here we found that maternal alcohol consumption of up to 32g/week was associated with an 10% increased risk of preterm birth. In comparison, light to moderate smoking (up to 20 cigarettes per day) is associated with a 22% increased risk of preterm birth.
‘Odds of small for gestational age (SGA) and preterm birth were higher for babies whose mothers consumed up to 32g/week versus none, but estimates for preterm birth were also compatible with no association,’ the review said.
The review noted the lack of the evidence on light drinking: ‘Evidence of the effects of drinking up to 32g/week in pregnancy is sparse.’
However, ‘as there was some evidence that even light prenatal alcohol consumption is associated with being SGA and preterm delivery, guidance could advise abstention as a precautionary principle but should explain the paucity of evidence,’ they concluded.
Due to the lack of clinical data, health practitioners are unable to recommend a ‘safe’ level of alcohol during pregnancy and therefore should advise abstention, the researchers suggested.
The researchers systematically reviewed all the data from a 26 observational studies on the impact of light drinking (two units up to twice a week, or four units a week, equivalent to a total of around 32g) compared with no alcohol at all.
They looked particularly at complications of pregnancy and birth characteristics, such as miscarriage, premature birth, and undersized babies, and longer term issues, such as the developmental delays, impaired intellect, and behavioural difficulties typical of fetal alcohol syndrome – a consequence of heavy drinking in pregnancy.
Until recently UK guidelines advised women to avoid alcohol while trying to conceive or in the first trimester, but also indicated that consumption should be restricted to one to two units, once or twice a week.
International guidelines currently recommend that pregnant women abstain from heavy or ‘binge’ drinking.
Following a commissioned review by the UK chief medical officer (CMO), the new proposed guidelines indicate that women should ‘abstain from all alcohol when pregnant or trying to conceive, based on the precautionary principle of ‘better safe than sorry’, in the absence of robust evidence.’
The issue remains of great public health importance as up to 80% of pregnant women in the UK, Ireland, New Zealand and Australia drink some alcohol during their pregnancy.
‘Women who have had a drink while pregnant should be reassured that they are unlikely to have caused their baby considerable harm, but if worried, they should discuss this with their GP or midwife,’ the researchers said.
‘Despite the distinction between light drinking and abstinence being the point of most tension and confusion for health professionals and pregnant women, and contributing to inconsistent guidance and advice now and in the past, our extensive review shows that this specific question is not being researched thoroughly enough, if at all.’
‘Limitations of the science’
Dr Daghni Rajasingam, spokesperson for the Royal College of Obstetricians and Gynaecologists (RCOG) said: ‘As there is no proven safe amount of alcohol women can drink during pregnancy, abstinence is the safest option, particularly for women trying to conceive or those in the first three months of pregnancy. While this study adds to the evidence that drinking 1-2 units of alcohol a week after the first 12 weeks of pregnancy is unlikely to have a harmful impact on the baby or pregnancy, we cannot rule out the risks altogether.
‘It’s important that women are informed about the risks associated with heavy drinking during pregnancy, including fetal alcohol spectrum disorders and an increased risk of miscarriage, but healthcare professionals should also be open and honest about the limitations of the science in relation to drinking 1-2 units a week during pregnancy, supporting them in coming to a decision for themselves.’