2012/01/13 by Susan Morton, Polly E. Atatoa Carr, Cameron Grant +14 · 2 citations
Medicine · Decision Sciences · Social Sciences · #Birth, Development, and Health #demographic modeling and climate adaptation #Health disparities and outcomes
paper · pdf · doi:10.1093/ije/dyr206
openalex publication_date 2012/01/13 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/01
The longitudinal study, ‘Growing Up in New Zealand’, was explicitly established to provide contemporary, population-relevant evidence about the multi-disciplinary determinants of pathways towards health and development for children born in the 21st century New Zealand. Improvements in child health have been slower in New Zealand in recent decades relative to other developed countries, and in 2009 New Zealand was ranked 29th out of 30 OECD countries.1 Examples of child health indicators where New Zealand performs relatively poorly include infant mortality rates, immunization coverage, accidents and injuries in under 5-year-olds, rates of child maltreatment and hospital admission rates for a spectrum of communicable diseases including pertussis, pneumonia and rheumatic fever.1–4 Compared with other OECD countries, New Zealand also has a poor record with respect to the proportion of children living in households below the poverty line, as well as for measures of income inequality.5–7 There are also inequities in health and developmental outcomes within our child population, with poorer outcomes in general for New Zealand's indigenous (Māori) children, children of families from Pacific Island nations, and those living in socio-economic deprivation. These disparities exist across a broad range of measures including those for which effective prevention strategies are known, such as vaccine preventable disease and rheumatic heart disease.4 Despite expensive well-intentioned interventions, inequalities have remained, and in many cases widened.8–10 Earlier longitudinal studies in New Zealand have shown the adverse long-term effects of disadvantage in early childhood on subsequent health outcomes.11,12 These historical studies have had considerable scientific and policy utility. However, the new generation of New Zealanders are more diverse than those of the historical cohorts in terms of ethnic identity, family structures and contextual environments. Therefore, a new longitudinal study was deemed necessary to determine pathways of development for the diverse group of contemporary New Zealand children, as well as to address the origins of now well-described, but still poorly understood, inequities in health outcomes according to ethnic identity. Accordingly, the New Zealand Ministry of Social Development and several other government agencies commissioned a new longitudinal study in 2004. This study was launched as ‘Growing Up in New Zealand’ in April 2008 following an extensive peer-reviewed development phase, and ethics approval was obtained from the Ministry of Health Northern Y Regional Ethics Committee. ‘Growing Up in New Zealand’ has been designed as longitudinal from the outset; it is multi-disciplinary in nature and includes a translational dimension, with an explicit intent to both relate to the current policy context and inform future policy development. The four overarching objectives are to: map the developmental trajectories for a cohort of New Zealand children, in order to identify the main causal pathways, and the links between them, across multiple levels of influence (political, social, cultural, intergenerational, familial and individual) for outcomes in key social, developmental and health domains across the lifecourse; describe cross-sectional outcomes (in several domains) at key points in the lifecourse of the developing child to enable comparisons between subgroups and within subgroups (including by ethnic identity), and with international populations; focus on factors and trajectories, across multiple levels of influence, that confer resilience and optimize development, rather than focusing solely on risk factors for poor outcomes and; identify critical periods in development, and levels of influence, that will allow the development of policy directed at optimising the lifecourse development of every child born in New Zealand. This will build on the demonstrated value and lessons learnt from earlier New Zealand longitudinal studies, while reflecting the scientific and demographic changes that have occurred since the earlier studies began. In particular ‘Growing Up in New Zealand’: considers both antenatal and intergenerational influences on child development (recruiting in pregnancy and beginning data collection before birth); emphasizes the importance of early life data (four data collection points in the first 2 years of life); includes data collected independently from fathers (and partners) from before birth; provides an ethnically diverse cohort relevant to current New Zealand births; takes an interdisciplinary and lifecourse approach to child development; has developed relationships with multiple stakeholders, notably with policymakers, to facilitate timely translation of research findings. The conceptual framework for ‘Growing Up in New Zealand’ takes a lifecourse approach to child development and therefore recognizes the dynamic interactions between children and their environments across a broad range of influences from their immediate family environments to their wider societal contexts over time (Figure 1). Conceptual framework for understanding child development in ‘Growing Up in New Zealand’ The sampling strategy was designed to recruit a cohort of children from before their birth so that evidence on their developmental trajectories over time would be broadly generalizable to the current population of New Zealand births. Other considerations included: the challenge of antenatal recruitment in the absence of a register of all pregnant women; the need to recruit across a time period to allow for seasonal variation; the need for size and diversity to allow subgroup analyses, particularly by ethnic identity and; the constrained fiscal environment. Sampling births within a defined geographical region provided the most cost-efficient and effective strategy for cohort recruitment and retention for future data collections (although follow up will not be limited to the recruitment areas). The geographical area chosen for recruitment, after due consideration, was the region of the North Island covered by the three contiguous District Health Boards (DHBs) of Auckland, Counties-Manukau and Waikato. The most up to date birth statistics available to inform the 2008 recruitment strategy were all New Zealand births from 2003 to 2007. Using data for 5 years of births avoided anomalies in birth statistics in any one particular year. These indicated that 29% of New Zealand's population resided within and over one-third of New Zealand's live births occurred in the chosen recruitment region.13 The three DHB areas were primarily chosen to maximize the diversity of participants to ensure that the recruited cohort would be broadly generalizable to New Zealand's current population of births, particularly in terms of maternal ethnicity, markers of parental socio-economic position and mix of urban or rural home environment. All pregnant women living in the three DHB areas with an estimated delivery date between 25 April 2009 and 25 March 2010 were eligible to be recruited. Given the lack of a register of pregnant women, the challenge was to ensure that all eligible pregnant mothers living in the selected recruitment region received a timely invitation for their child/children to participate. In order to address this challenge, multiple recruitment strategies were employed. Over 99% of all pregnant women in New Zealand engage with a Lead Maternity Carer (LMC) during their pregnancy, so a key recruitment strategy was using LMCs (independent midwives, obstetricians, hospital midwives and family physicians) in the study region to provide information on ‘Growing Up in New Zealand’ to eligible pregnant women. The LMCs sought verbal permission from the women to provide their contact details to the recruitment team who could then invite them (and their future children) to participate in the study. In the initial stages of recruitment, this was the only strategy with ethics approval. However, during piloting this was found to be insufficient for recruitment of the required sample. Complementary strategies, initiated once ethical approval was obtained, involved working with community organizations and media (both universal and targeted) to inform all eligible women about the study. The women could then contact ‘Growing Up in New Zealand’ directly (by text message, free phone and via the internet) to indicate their interest in participating. In addition, a team of recruiters maintained a presence in all hospital and community antenatal clinics throughout the recruiting period, and also attended community events and activities across the sampling area. Strategies were revised regularly throughout the recruitment period to ensure effectiveness and efficiency at recruiting the required generalizable cohort, particularly with respect to maternal characteristics such as self-identified ethnicity and area of residence. In total 10 315 referrals of pregnant women were received. When contacted, 6822 (66%) mothers consented to their children participating in ‘Growing Up in New Zealand’ for 21 years. The resulting cohort of 6846 children (live births) provides adequate statistical power to undertake complex analyses of interlinked developmental trajectories over time across the whole cohort of children as well as within subgroups of children who are expected to identify themselves as Māori, Pacific and Asian (at least 1000 children in each of these subgroups). The size of the recruited cohort at baseline was also calculated to allow for adequate power after the anticipated attrition (of up to 15%) in the first 2 years of the study.14 Although routine New Zealand-wide birth statistics are as yet incomplete for the recruitment period (2009–10), based on the latest data available from Statistics New Zealand, the demographic characteristics of the mothers of the recruited cohort are comparable with those of all New Zealand parents with respect to key parameters such as distribution of maternal age, ethnicity, parity and area level deprivation (Table 1). The proportion of children born to mothers who were born elsewhere has been increasing and the distribution of birthplace of the ‘Growing Up in New Zealand’ mothers highlights this trend.16 Comparative baseline characteristics of the cohort of pregnant women enrolled into ‘Growing Up in New Zealand’ aIncludes multiple response(s) and will total to >100%. bBased upon the 2006 New Zealand index of deprivation.15 cHospital based maternity events report 2007 does not include this information. Comparative baseline characteristics of the cohort of pregnant women enrolled into ‘Growing Up in New Zealand’ aIncludes multiple response(s) and will total to >100%. bBased upon the 2006 New Zealand index of deprivation.15 cHospital based maternity events report 2007 does not include this information. When mothers agreed to scheduling an antenatal interview they were also asked to provide the contact details for their current partner (defined as the partner she was currently in a ‘significant social relationship with’). Partners were contacted independently to invite their participation. A total of 4404 partners consented and completed an antenatal interview. Over 99% stated at the interview that they were the biological father of the cohort child. The paternal characteristics are further detailed in Table 2. Baseline characteristics of the partners in ‘Growing Up in New Zealand’ aIncludes multiple response(s) and will total to >100% Baseline characteristics of the partners in ‘Growing Up in New Zealand’ aIncludes multiple response(s) and will total to >100% Four data collection waves (DCWs) were explicitly planned for the first 2 years of the study to collect detailed information to describe trajectories of early life development from before birth (Figure 2). Data collection for ‘Growing Up in New Zealand’ during the first 2 years The first DCW was completed in June 2010. This consisted of a face-to-face Computer Assisted Personal Interview (CAPI) with the pregnant mother (most often in the last trimester of her pregnancy) and with her partner independently, most often in their own home. The second face-to-face CAPI with mother and partner took place when the cohort children were 9 months old and was completed in January 2011. The third face-to-face CAPI (when the children are 2 years old) commenced in May 2011 and also involves direct observations and developmental and anthropometric assessments of the children. Linkage to routinely collected perinatal health records was also completed in 2011, providing information about the latter stages of pregnancy, birth records and immediate neonatal outcomes. Further linkage to routine health records is ongoing (Table 3). The next face-to-face data collection is planned for when the children are ∼4 years of age. Linkage to routine data sources in first 2 years of ‘Growing Up in New Zealand’ aIn New Zealand vaccines are scheduled for ages 6 weeks, 3, 5 and 15 months.17 Linkage to routine data sources in first 2 years of ‘Growing Up in New Zealand’ aIn New Zealand vaccines are scheduled for ages 6 weeks, 3, 5 and 15 months.17 Brief Computer Assisted Telephone Interviews (CATI) were utilized when the children were ∼6 and 35 weeks, 16 and 23 months old (Figure 2). Further CATIs are planned for when the children are ∼31 and 39 months old. These 5-min contacts with the child's mother (or equivalent) allow for age-appropriate developmental information collection and assist with cohort retention. Given the study's conceptual framework for child development (Figure 1) each DCW seeks information across six interconnected domains: family and whānau (extended family), societal context and neighbourhoods, education, health and well-being, psychological and cognitive development, and culture and identity. Each cross-sectional DCW is planned according to a balance of age-appropriate information from all the interconnected domains, in the context of the overarching longitudinal research objectives, while being as policy-relevant as possible. Attention is also given to ensuring that the methods utilized to collect domain-specific evidence acknowledge the unique New Zealand population and environmental context. In particular, the integration of the Māori theme as well as the Kaitiaki (guardianship) advisory group provides a unique opportunity to examine the factors which contribute to the well-being of Māori tamariki (children) and their whānau over time. The overall integration of information is represented by the weaving of a kete (basket)—metaphorically holding all the elements necessary for life (Supplementary Figure S1, available as Supplementary data at IJE online). A summary of constructs measured is provided in Table 4. The ‘Growing Up in New Zealand’ construct map up to 2 years of age M: mother; P: partner; CP:child proxy. The ‘Growing Up in New Zealand’ construct map up to 2 years of age M: mother; P: partner; CP:child proxy. The pregnancy outcome from the 6822 pregnant women who completed the antenatal interview was determined at the CATI call made 6 weeks following the estimated delivery date. A total of 6846 live births therefore make up the participant cohort for ‘Growing Up in New Zealand’. A small number of pregnant women experienced perinatal (late feetal and neonatal) loss and the cohort includes multiple births (Figure 3). Retention of the child cohort of ‘Growing Up in New Zealand’ study at the 9-month data collection wave (November 2011) At the 9-month DCW, information was gathered from 94.5% of the child cohort. When it was not possible to complete this interview, the opportunity to skip that DCW and return to the study at a later time was taken on behalf of 320 children (4.7%). The antenatal findings from ‘Growing Up in New Zealand’ highlight the diversity of the new generation of New Zealand children. Many of the parents of this cohort moved to New Zealand in their adult years, with one-third of children having at least one parent who was not born in New Zealand. Eighty percent of the households use English as their primary language for everyday conversations at home, and a wide range of languages are spoken in the remaining households. Many families are highly mobile (over half had moved twice or more in the last 5 years), and almost half of all families were living in rental accommodation when their child was born. Over a third of all parents of the cohort have tertiary level qualifications and the average parental age increased with increasing qualification level (Table 5). Over half of all pregnant women were employed during the last trimester of their pregnancy. The majority (80%) of partners of pregnant women were employed, with 7% either unemployed (actively seeking employment) or not in the workforce by choice. Highest educational qualification of the mothers and partners enrolled into ‘Growing Up in New Zealand’ Highest educational qualification of the mothers and partners enrolled into ‘Growing Up in New Zealand’ Sixty percent of the pregnancies were described as planned. Just over 5% of mothers in the later stages of pregnancy were not in any relationship. Many of the children of this cohort will have older siblings (Table 6). Pregnancy intent, relationship status and index child's birth order for the ‘Growing Up in New Zealand’ mothers Pregnancy intent, relationship status and index child's birth order for the ‘Growing Up in New Zealand’ mothers Summary information regarding the antenatal findings of ‘Growing Up in New Zealand’ are available on the website www.growingup.co.nz in the report ‘Before we are born’.18 In addition, a range of publications are underway, including topics such as health and well-being of parents during pregnancy, family structures and relationships in contemporary families, sources of formal and informal support for families and parents during pregnancy, adherence to nutritional and behavioural guidelines in pregnancy and parents’ postnatal intentions and lifecourse expectations for their children. In addition to the explicitly lifecourse and longitudinal design and objectives of ‘Growing Up in New Zealand’, the antenatal recruitment and data collection from mothers and partners a of the study. This has the collection of detailed information on during pregnancy on use of health and of and as well as intentions for postnatal The cohort size and diversity provides adequate power to examine complex developmental lifecourse outcomes across the whole population as well as within particular population including by ethnic identity. this study will be to provide contemporary evidence to inform to the and increasing disparities in health and well-being outcomes within the New Zealand The antenatal and face-to-face of partners is a of ‘Growing Up in New Zealand’. a small number of other contemporary longitudinal studies have many not recruit in of partners on the of the mother to provide contact information and they are not generalizable to all fathers of in New Zealand. their from before birth is unique in the New Zealand context. The of a with geographical was the and of recruiting and a cohort were There are several to the recruitment strategy The region and the development of a identity for the being of an defined birth cohort has an focus for retention strategies in other longitudinal The chosen region also provided the opportunity to recruit a diverse cohort most to be generalizable to the current birth population with respect to key parental and family ‘Growing Up in New Zealand’ has links with policy working with multiple government agencies and throughout the development, and These relationships will enable findings to be in a timely to inform relevant population strategies to child health and is that the ‘Growing Up in New Zealand’ data be by and policy to from this Data from that the terms of data will be from for the antenatal The were designed to the and the of the longitudinal over time. Further details about for data and for data be obtained the website The primary and government for this study to date has been the New Zealand Ministry of Social Development the Ministry of Health and The of have the most and support to the to date. Other agencies have also include the of and and Pacific Island the of and of Māori the New Zealand and New Zealand, New Zealand and the Health has also been provided by and the Health in the development of the study. is currently not June with any or to to to collect and provide longitudinal developmental information for the current generation of New Zealand children. Supplementary Data are available at IJE we would to acknowledge the children and the families who are of the ‘Growing Up in New Zealand’ study. would also to acknowledge the initial in particular the New Zealand Ministry of Social by the Health as well as the ongoing support from and the of The of this are of the current research team including the study and the and theme acknowledge all the of the ‘Growing Up in New Zealand’ including those and of the and community and of the study. the ongoing support and provided by our Kaitiaki and our and international and we also acknowledge the of the for and design of this study in the development of ‘Growing Up in New Zealand’ is a longitudinal study commissioned by the of New Zealand in designed to the translation of research evidence to inform policy development. A cohort of 6846 children born between March 2009 and May 2010 was enrolled via their pregnant were for pregnant mothers as well as their and further face-to-face occurred when the child was 9 months and are at 2 years of age. Brief phone collected further information when the child was 6 and 35 weeks, 16 and 23 The size and diversity of the cohort provides an opportunity to examine developmental trajectories for the whole cohort of children as well as within subgroups who identify as Māori, Pacific and