The Growing Up in New Zealand cohort

The Growing Up in New Zealand cohort is made up of around 7,000 children who were recruited from all expected births in the Auckland, Counties-Manukau and Waikato District Health Board regions between 25 April 2009 and 25 March 2010.

In total, 6822 pregnant women and 4401 of their partners were recruited into the main cohort. An additional 200 families form the so called "Leading Light: Te Roopu Piata" group. Leading Lights are about six months older than the main cohort and ensure that the information we collect is fit for purpose, and that it works with our diverse children and families.

The ethnicity and socio-demographic characteristics of the children and families in the cohort are broadly generalisable to those of children being born in New Zealand today. The size and diversity of the cohort is one of its key strength and an important feature to make the information we collect as useful as possible for policy development and research.


Particular strengths of the Growing Up in New Zealand cohort

  • The cohort is broadly generalisable (in terms of diversity of ethnicity and markers of family socio-economic status) to contemporary New Zealand births. It is therefore able to provide longitudinal information generalisable across all contemporary NZ families with pre-schoolers.

  • The cohort is seven to ten times larger than those of the two major historical cohort studies conducted previously in New Zealand. This size is now considered standard to investigate developmental pathways for diverse groups within a population.

  • The cohort reflects today's children rather than the overwhelmingly European cohorts of children recruited into the previous longitudinal studies nearly 40 years ago (in the 1970s). It includes approximately 1700 children who identify primarily as Māori (24%), 1200 who identify as Pacific (21%) and 1000 (16%) as Asian, in addition to 66% who identify as European or Other. Nearly half of all the children identify with more than one ethnic group.

This diversity of children, and the numbers of children in each ethnic group, provides the capacity to understand why we see such different developmental pathways and inequalities in health and wellbeing outcomes across different groups of children.


The cohort at the time of recruitment (pre-birth)

The mothers

  • When giving birth to the cohort child, they are aged from 15 to 47, with an average age of 30.

  • 49% identify as NZ European, 18% as Māori, 15% as Pacific and 15% as Asian.

  • Over a third can speak more than one language, with one in five speaking a language other than English at home.

  • Nearly half are first-time mothers.
  • 5% are teenagers.

  • 40% of the children were not planned.

  • 10% had some fertility assistance to get pregnant.

  • Just over 5% of mothers were not in a relationship during late pregnancy.

  • More than half of the mothers were working in the last trimester of their pregnancy.


The fathers

  • Our fathers are aged from 16 to 64, with an average age of 33

  • 57% of our fathers identify as NZ European

  • 15% identify as Māori

  • 12% identify as Pasifika

  • 14% identify as Asian

  • More than 80% of fathers were working when mum was in the last trimester of this pregnancy.

  • Almost a third of fathers can speak more than one language.


The parents

  • 97% can have a conversation in English.

  • More than a third have tertiary education qualifications.

  • 8% of mothers and 12% of fathers are students.

  • The most usual languages spoken at home after English are Samoan, Hindi, Tongan and Mandarin.

  • Nearly 63% of our parents are either married or in a civil union.

  • The median household income in the year before the children were born was between $70,000 and $100,000.


When the mothers were pregnant

  • 90% made some changes to their diet.

  • 16% did not take folate at any time before or during their pregnancy.

  • More than one in 10 mothers continued to smoke once they knew they were pregnant.

  • Many kept drinking some alcohol throughout their pregnancy.

  • The majority of mothers stated that they hoped to breastfeed until their child was at least six months old.

  • Most mothers (85%) planned to immunise their children, but 3% didn't and 12% were undecided.


Read the full cohort profile in our Before we are born report