Hello, I write patient information leaflets about use of medicines etc in pregnancy for my job. These are based on the most up to date scientific evidence. I wrote the alcohol leaflet last week, although it hasn't been released yet as it is still being edited. I will post a link when it is out if anyone is interested. As with any exposure in pregnancy, it is up to the individual to weigh up the benefits against any possible risks.
Here is the low down on alcohol
(1) there is very strong evidence that heavy drinking is harmful and can cause both physical birth defects and learning and behavioural problems in the child (but you probably knew that anyway!)
(2) the evidence on binge drinking and occasional drinking is less clear cut, with some studies showing effects and others not. There are a lot of problems with these studies that may make the results unreliable, including that women may under report their drinking, and other lifestyle factors that are not taken into account can affect pregnancy outcomes and neurodevelopment in the child
(3) however, there are a small number of studies that have shown possible effects on learning and behaviour with low levels of alcohol (with the caveats described above)
(4)it is a fact that there is no safe proven level of alcohol in pregnancy
(5) it is possible that genetic variation between individuals might mean that some babies are more susceptible than others to the effects of smaller amounts of alcohol
Just to comment on some of the discussion above, the baby's brain continues to develop right to the end of pregnancy so only avoiding in the first trimester will not protect against any possible neurodevelopmental effects
The way I have been taught is that alcohol does cross the placenta straight to the baby, and because the baby's liver is not fully developed, the baby's blood/alcohol level can actually end up higher than the mother's.
I do worry about the basis of the alcohol advice given in the 'Expecting Better' book, because many people seem to have latched onto it. The author quotes a study where low levels of alcohol have been linked to behavioural problems in children, and says that the results are flawed because the group of women drinking alcohol were also more likely to have used cocaine, which she says is known to cause neurodevelopmental problems in children. In fact, this is not true, we do not know whether or not cocaine does this. It could equally be the alcohol. The bottom line is that we just don't know.