"If we've got mums in the neo-natal unit, they have to fill one out for themselves and one for their babies, even if they're only one day old."
Ms Newton said hospital staff would fill out their forms at home.
Census collectors - 93 of them in Wanganui - will be out collecting census forms tonight. People also have the option of filling in their forms online.
Last held in 2006 and conducted every five years since 1851, the census has been delayed only three times - due to the Depression in 1931, World War II in 1941 and the deadly Christchurch earthquake in 2011.
This year's survey is estimated to cost $72 million, slightly less than the $90 million budget for the 2011 census because much of the preparation was already done.
An official count of the people in New Zealand goes back as far as 1842. However, New Zealand's first official census was in 1851.
That survey asked questions on aspects of life just as it does today - including ethnicity, education, and disability.
It counted only European settlers, however, and a separate Maori census was taken from 1857 to 1858.
From 1874, the Maori censuses occurred around the same time as the European censuses until the two were integrated in 1951.
Several topics must, by law, be included. Under the 1975 Statistics Act every person in New Zealand on Census Day is asked their name and address, sex, age and ethnicity.
Over time, questions have been added and omitted in line with what was considered salient by government departments at the time.
The 1906 census asked for the number of poultry - geese, ducks, fowls, turkeys or other - the number of beehives, and the amount of honey and beeswax they produced in a year.
From 1936 to 1971 questions about war participation were asked, and in 1971 people were asked whether their dwelling had flushing toilets, telephones, fridges, deep freezes or powered lawnmowers.
The information gathered is used by businesses, iwi, councils, and the government to make decisions on issues that affect the country.
Billions of dollars of decisions are made in areas including health, education and transport, based on the data gathered.