Researchers have found no association between pregnant women's exposure to the mine fire smoke of 2014 and low birth weights or premature births.
They are the first findings from the Hazelwood Health Study's Early Life Follow-Up Cohort Study which gathered data on Latrobe Valley infants who were up to two-years-old at the start of the fire and mothers who were pregnant during the fire.
Researchers also assessed children conceived after the fire to use as comparison data as they were not exposed to the Hazelwood mine fire, which burnt for nearly six weeks.
The study exceeded its target of 500 by 48 people.
Menzies Institute of Medical Research public health physician Shannon Melody said the results were "reassuring", yet more needed to be done to validate the findings.
"We were very thankful we met our recruitment target ... but because the Latrobe Valley is not a very large population, there's only so many people we can recruit, so it just means the statistical power of the study is limited," Dr Melody said.
"It means that we might not see an association between the smoke event and birth outcomes when one truly might exist."
The study has begun looking at the government's routinely collected birth data from across the state in the period before and after the fire to draw more definitive conclusions about whether or not the fire affected birth outcomes.
Examining state-wide data will help to highlight whether risk factors such as smoking during pregnancy correlated with lower birth weights.
Dr Melody said smoking was well known to affect an unborn child.
"We certainly saw that in our study," she said.
"Women smoking during pregnancy are more likely to have smaller babies, which highlights the importance of looking after mothers in pregnancy and having access to health services and Quit programs to optimise that period and support them."
About 18 per cent of mothers in the study reported smoking whilst pregnant, which is higher than the national rate of 11 per cent.
Stress was another risk factor.
Dr Melody said her team asked women in the study how stressed they were during pregnancy and the mothers who reported being stressed most or all of the time tended to have smaller babies and there was an increased risk of babies being born earlier.
"That fits with ... other studies we see overseas as well as in Australia," she said.
Dr Melody said the findings filled in an "important knowledge gap".
"No previous studies have been done on what an event like this; one, being a coal mine fire and two, being a smoke event [of] six weeks had on pregnant women and their children," she said.
She said her team looked forward to the ongoing participation of Latrobe Valley families.
Another clinic in 2020 will repeat last year's heart and lung checks to provide a follow-up on the same children.
For more about the study findings, go to hazelwoodhealthstudy.org.au/study-findings.