During training on foetal alcohol syndrome with a paediatric consultant and a social worker, they said that it isn’t necessarily the volume consumed, it is dependent on the point in development of the foetus.
Obviously, women who drink heavily are more likely to drink on days in which crucial development takes place, than those who don’t drink heavily. So, the more you drink, the more likely the foetus will be affected.
But..... Technically, you could get totally drunk 3 or 4 times, and not affect the development at all, due to the days you consumed alcohol, but another pregnant woman could drink lightly on just one day, and affect the growing baby.
An example they gave was the formation of the mouth and nose - if the mother drinks during this window of development, then a physical effect may be seen. If they drink heavily, but not in this window of development, the mouth and nose may develop normally.
Some children with foetal alcohol syndrome can therefore have the physical effects, but others may not - for example brain development isn’t externally visible - it could be later that cognitive defects or behavioural issues become known.
The advice they gave was don’t drink at all, it’s very difficult to know when it will be safe.
They also said, the amount you consume is multiplied by 3 for the baby - if you drink half a glass, your baby is affected by the equivalent of 1 and a half glasses, due to their inability to process alcohol.
They said in terms of long term impact, heroin has fewer long term physical effects. Clearly having a parent who is an addict, will impact greatly on a child, but purely on a physical basis, the baby can be weaned off the hard drugs, but the impact of alcohol is irreversible.
www.fasdnetwork.org/what-is-fasd.html