"We don't know how much one individual glass is going to do during development but we know it's not going to do good stuff."
For a child to have foetal alcohol spectrum disorder, (FASD) a woman would usually have to have a lot more than one glass during pregnancy, Ms Rogan said.
But, she said, that's not the same thing as doing no damage.
"There's no such thing as a safe neurotoxin. It's impossible to measure down to minute degrees of damage. The reason it's impossible is you can't predict individual potential.
"You don't know how much potential we could have had if our mothers didn't drink.
"Most kids who get exposed to small amounts of alcohol are okay, but are they the best they could have been? Probably not."
Tauranga Hospital midwifery manager Esther Mackay said drinking while pregnant can have a wide range of impacts.
"No level of alcohol use in pregnancy is considered safe. And all mothers-to-be will be exposed to that messaging during their pregnancies.
"Foetal alcohol spectrum disorder is a general term used to describe a wide range of effects that can occur in an individual who was exposed to alcohol in pregnancy. The effects include physical, mental, behavioural and learning difficulties, with lifelong implications."
Ms Mackay said referral to addiction agencies was recommended if alcohol was regularly consumed in pregnancy and the Ministry of Health has provided a screening tool for lead maternity carers to use when talking to their clients about alcohol.
Tauranga midwife Nell Hurst, an independent lead maternity carer with Bay Births, said alcohol exposure in pregnancy could result in miscarriage, premature birth or stillbirth or a baby being born with growth restriction, developmental delay or birth defects.
"The effects alcohol has on their unborn child I feel is well advertised, or maybe it is because women are better educated due to perhaps seeking a midwife early in their first trimester ofpregnancy.
"In my experience most women appear very aware of the risks caused by alcohol on the growing foetus and therefore find it easy to not drink while they are pregnant."
Ms Hurst said she was surprised by the report's findings that up to 80 per cent of women had consumed alcohol at some stage in their pregnancy.
"A large number of women who are not trying to conceive may drink in the early weeks before they even realise they are pregnant, but they do this unknowingly and are often concerned about the effects the alcohol they have consumed in those early weeks will have on their unborn; only wanting what is best for their baby."
Ms Hurst said babies whose mothers used or abused drugs or alcohol during their pregnancy often needed special care and were high risk.
"I imagine these women were born into a similar environment."
Bay Midwifery Centre lead maternity carer Bev Ward said her take was the majority of women avoided alcohol when pregnant.
Mrs Ward said when a woman did drink while consciously knowing she was pregnant, there was usually a background situation and right or wrong, they continued their drinking.
"In my field, the reason is usually through domestic violence. There is usually already a history of drinking, smoking or drugs, or a mental health illness."
"The ones that are really entrenched don't know how to get help. We want that woman to be safe and we want the baby to be safe, but we can't always make relevant changes because the woman will do what she does to survive and for her to get through means having a drink."
Cath Edmondson, Health Promotion Agency manager of policy and advice, said there was no known safe level at all to drink during pregnancy.
"There are risks in terms of not just FASD for the child, but miscarriage, stillbirth, premature birth and reduced birth weight."
Ms Edmondson said any woman who might have had alcohol before she knew she was pregnant should talk to a health professional with any concerns.
The facts
Why is alcohol use an issue during pregnancy?
•Drinking alcohol during pregnancy can result in miscarriage, stillbirth and a baby being born with a range of life-long effects.
•In the child, alcohol exposure in pregnancy can result in premature birth, brain damage, birth defects, growth restriction, developmental delay, and cognitive, social, emotional and behavioural deficits.
•It is estimated that between 600 and 3000 New Zealand babies are born every year with foetal alcohol spectrum disorder (FASD).
•Alcohol passes freely through the placenta and reaches concentrations in the baby that are as high as those in the mother. However, the baby has limited ability to metabolise alcohol. Alcohol and acetaldehyde can damage the developing baby's cells. Alcohol can also impair placental blood flow to the baby, leading to hypoxia.
Source: Health Promotion Agency
•Foetal alcohol spectrum disorder
A spectrum disorder describing a range of adverse effects caused by prenatal alcohol damage to the development of the brain.
•Physical effects:
Can include facial dysmorphology, growth deficits and other health problems.
•Cognitive effects:
Difficulties in processing information
Academic, social and developmental immaturity
Impulsive
Doesn't learn from experience
Impaired memory retention
Poor reasoning and judgment
Rage
Lack of cause and effect thinking
Inflexible thinking
Difficulties with money and time concepts
IQ higher than other brain domains
Hidden talents and strengths
Source: Foetal Alcohol Network NZ
