Hundreds of children are injured, killed or abused every year by caregivers who have been drinking but agencies are failing to grasp the extent of the problem, experts say.
An Alcohol Action conference on children and alcohol in Wellington today heard how the true extent of the problem was unknown because of a lack of reliable statistics on alcohol harm to others.
Otago University head of preventive and social medicine Professor Jennie Connor said most of the information routinely gathered by government agencies, social workers and hospitals did not include such data.
"Of course we don't need more data in order to do something about these problems but the gaps in knowledge are important because we get a biased idea of the impact of alcohol, and we need the information in order to be strong advocates," she said.
"We carefully carry out surveillance of things like infectious diseases in New Zealand, and we collect this information so that we can act on it. We can identify trouble spots, we know what the trends are.
"We don't do this for alcohol-related harm to others. We need to."
Prof Connor said her research found hospital emergency departments had no systematic way of collecting data on alcohol-related injuries, even for patients who caused the harm to themselves.
And Child, Youth and Family was unable to supply data on how widespread alcohol use was in cases of neglect or emotional, sexual or physical abuse.
Prof Connor's research team asked CYF for statistics but the request was declined because the agency's data was of insufficient quality for the researchers to use.
A study in Australia found a third of child abuse cases in Australia involved alcohol use by the offender.
"If we translated that into the New Zealand numbers, that would be 4000 cases a year where alcohol affected the outcome - but we don't know how comparable the reporting data is," Prof Connor said.
Among the most worrying gaps was the lack of reliable, routinely collected data on the prevalence or severity of fetal alcohol spectrum disorder (FASD).
Overseas studies have found up to five per cent of babies may be affected by FASD, which would equate to 600 to 3000 cases a year in New Zealand.
What is known about the extent of the problem has had to be gleaned from surveys.
Prof Connor pointed to unpublished research from Otago University colleague Simonette Mallard, who conducted interviews with new mothers at maternity units nationwide.
The research found only 37 per cent of drinkers abstained before attempting to become pregnant, and only 17 per cent of heavy drinkers - women who had more than five drinks per day on average - did so.
A quarter of all drinkers continued to drink after they became pregnant, while 12 per cent of all pregnancies involved heavy drinking in the early stages of pregnancy.
Prof Connor also pointed to a recent survey in which 17 per cent of respondents indicated children had been negatively affected by someone else's drinking in the past 12 months.
Some 11 per cent said the child had been yelled at or hit, while seven per cent of children had witnessed serious violence.
"These are not small numbers," she said.
Child and youth mortality review committee chair Dr Nick Baker said alcohol was likely a factor in many accidental deaths, including sudden infant death syndrome.
"New Zealand has very poor data at present on the level of alcohol involvement in these sorts of deaths," he said.
"The only mention about alcohol in this sort of case is the police report or coroner commenting about empty bottles around the house. Almost never would blood samples be taken from those involved in this sort of death."
He called for blood samples to be taken from caregivers in all cases of accidental child deaths or serious injuries.
Children's Commissioner Dr Russell Wills said as a pediatrician, he saw increasing numbers of children suffering FASD.
"Pediatricians also see abuse and neglect of children and young people, and commonly we see the behavioural and developmental consequences of parents who have alcohol and drug addictions as well as mental illness," he said.
"There is no doubt that alcohol affects parenting capacity, and it means that they aren't able to respond to the emotional and developmental needs of children. And that has profound consequences."
Dr Wills called for monitoring of access to alcohol treatment services to ensure young people were seen first. He also called for hospitals to identify heavily drinking mothers to automatically refer them for treatment.