Researchers hope a study of 7000 children will help target assistance to those most in need, even before they are born.
In its latest report, the Growing Up in New Zealand study focused on what makes babies and toddlers more likely to get sick.
The study identified 12 risk factors associated with vulnerability to childhood illness, including poor quality housing, the mother's health, age and income.
It found one-third of children experienced between two and five risk factors in their first 1000 days of life, while 16 percent experienced 11 or 12 risk factors.
Lead researcher Dr Susan Morton hopes the risk factors can be used to get help to families most in need.
"What we could see is potentially a bit of a checklist, so that if mums are experiencing three or four or maybe five of these risk factors, that identifies that family and eventually that child as potentially a family that could do with a bit more support from early on."
The next stage of the study will look at why some children who are exposed to risk factors do not become ill.