Abstract

• Many pregnant women drink varying quantities of alcohol, although several guidelines recommend total abstinence.
   
• What is known of the dangers of alcohol for the outcome of pregnancy and for the unborn child? To answer this question, we conducted a review of the literature using the standard Prescrire methodology.
   
• Fetal alcohol syndrome, which combines facial dysmorphism, growth retardation and intellectual disability, occurs in about 5% of children who are regularly exposed to at least five standard units per day (about 50 g of alcohol per day).
   
• Four studies have explored the link between heavy maternal alcohol use over a short period and the risk of cognitive impairment in the child. The results were inconclusive, however, and the authors failed to take concomitant chronic alcohol consumption into account. A methodologically sound study showed an increase in neurological abnormalities (seizures and epilepsy) when the mother drank heavily during short periods between the 11th and 16th weeks of pregnancy.
   
• There is a risk of cognitive and behavioural problems in children whose mothers regularly drank more than 2 standard units per day
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• Studies involving a total of about 150 000 pregnancies sought a link between low-level alcohol consumption and abnormal pregnancy outcomes. Very few showed a statistically significant link, and the results are undermined by the failure to take other risk factors into account.
   
• Weekly consumption of 5 standard units or more during pregnancy has been linked to an increased risk of cryptorchidism. Studies in a total of 57 000 pregnancies showed no effect of minimal alcohol consumption on the risk of malformations. A study of 1000 pregnancies showed a statistically significant risk of major malformations, but there were several apparent biases.
   
• A link between infant mortality and alcohol consumption during pregnancy was examined in large cohort studies. Consumption of at least 4 standard units per week increased the risk of early neonatal death. Smoking further increased the risk. Daily alcohol consumption should be avoided during pregnancy.
   
• A face-to-face interview remains the best way of detecting at-risk drinking during pregnancy. Specific questionnaires (T-ACE and Tweak) can also be helpful.
   
• Women often spontaneously cut down on their drinking in early pregnancy. A clinical trial showed that women with at-risk drinking were more likely to reduce their consumption if they were informed of the risks for their pregnancy and their unborn child on several occasions than if they were simply given an information leaflet.
   
• In practice, women must be informed of the risks of alcohol consumption during pregnancy, but this must be done tactfully. The risks of minimal alcohol consumption should not be overstated.    

©Prescrire 1 January 2012

"Pregnancy and alcohol. Occasional, light drinking may be safe" Prescrire Int 2012; 21 (124): 44-50. (Pdf, subscribers only)