Alcohol during pregnancy - the issues

What evidence is being used?
The Department of Health has, until May 2007, issued guidelines that are similar to those of NICE; the news story has arisen out of the fact that the DoH has changed the guidelines, while NICE has not. As O’Brian notes in the BMJ O'Brian2007, the new DoH advice does not rest on any new evidence, but merely on the reinterpretation of the risk associated with the already known evidence. Therefore this particular news story centres not so much on conflicting evidence supporting two different points of view, but on two different interpretations of the same evidence.

Regarding this existing evidence, the references are not cited in the Pregnancy Book, nor is it cited in the public leaflets on antenatal care published by NICE (2003 version), or indeed on the FAQ list of the NHS direct website (which, like the Department of Health, advises complete abstinence). Furthermore, these books and leaflets do not provide any details of the evidence that is being used to reach the conclusion. As an extreme example, the DoH merely states that

The UK's Chief Medical Officers advise that, as a general rule, pregnant women, or women trying to conceive should avoid drinking alcohol. If you do drink while you are pregnant, it is better to limit yourself to one standard unit of alcohol a day (roughly the equivalent of a small glass of wine, a half pint of beer, cider or lager, or a single measure of spirits).

(DoH 2007: 14).

The old NICE guidelines were slightly more descriptive of the effect of alcohol on the child:

Research shows that heavy or frequent drinking can seriously harm your baby’s development. When you drink, alcohol reaches your baby through the placenta. But your baby cannot process it as fast as you can, and is exposed to greater amounts of alcohol for longer than you are. And too much exposure to alcohol can seriously affect your baby’s development and can cause Fetal Alcohol Syndrome. Children with this have restricted growth, heart defects, facial abnormalities and learning and behavioural disorders. The UK’s Chief Medical Officers advise that, as a general rule, pregnant women or women trying to conceive should avoid drinking alcohol. If you do choose to drink, to protect your baby you should not drink more than one or two ‘units’ of alcohol once or twice a week and should not get drunk.

(NICE, 2003a: 14)

The parallel NICE guidelines aimed at health professionals quotes the following referenced (in square brackets) evidence to support their advice that very moderate levels of drinking are safe:

Research evidence is consistent in finding no evidence of foetal harm among women who drink one or two units of alcohol per week.[106] There is also little or no evidence of harm in women drink up to ten units per week. However, binge drinking or otherwise heavy consumption of alcohol is associated with adverse baby outcomes such as low birthweight [107,108] and behavioural and intellectual difficulties later in life.[109] [Evidence level 3] Binge drinking is also associated with fetal alcohol syndrome and the incidence in Europe is reported to be 0.4 cases/1000.[110]

(NICE 2003b: 46)

Has there been a systematic review?

Yes, in the sense that both sets of guidelines rest on the same academic studies, as far as can be seen (the DoH Pregnancy Book does not cite evidence, see above).

Is there a numerical assessment of the probability of the outcomes?

Almost everyone involved admits that the risk is not easily quantified. The guidelines quoted stress that the studies are inconclusive as to the precise safe limit, and that therefore the precautionary principle applies (below).

If no formal analysis, is there an appeal to additional principles, such as the ‘precautionary principle’?

In this case the application of the precautionary principle by one agency but not another is the whole cause of the controversy.

How are the conclusions communicated?

Both DoH and NICE (as well as NHS direct) have published the advice in colourful leaflets/books that aim directly at giving digestible and succinct health advice to pregnant women. As such, these guidelines are part of the antenatal/pregnancy health awareness campaigns (as contrasted with alcohol awareness campaigns) that may contain similar advice, such as those offered by the Swiss Health Ministry or the guidelines offered by the New Zealand alcohol awareness council.

LINKS:

The 2003 NICE guidelines (pdf)
The draft NICE guidelines (October 2007) on which the newsreports above are based (pdf)
The current guidelines, March 2008 (pdf)
DoH pregnancy book May 2007