Birthweight of babies born in New Zealand

When the term 'people giving birth' is used, the numbers presented are births and are the number of people giving birth during the calendar year (ie, from 1 January to 31 December). A person who had twins or a multiple birth is counted as having had one birth. A person who gave birth twice within the same calendar year is counted twice.
The number of births presented includes only live births recorded in the Maternity Collection (MAT) at any gestation, and where a birth has a registration or birth record reported in the National Minimum Dataset (NMDS). Where a birth has an equivalent death registration recorded in the New Zealand Mortality Collection, the birth is also excluded from the analysis.

Each individual represented in the data is allocated to a single ethnic group, using the following priority system: Māori > Pacific peoples > Indian > Asian (excl. Indian) > Other > European. Individuals of European and of Other ethnicities are often grouped together and presented as being part of the 'European or Other' ethnic group due to small numbers in the ''Other' ethnic group.

It is important to note that the data collection actually includes all people who have given birth and that the data may include some transgender people.

From 1 July 2019, diagnoses codes are assigned using the 11th Edition of ICD-10-AM (International Statistical Classification of Diseases and Related Health Problems, Tenth Revision, Australian Modification) and procedure codes are assigned using the 11th Edition of ACHI (Australian Classification of Health Interventions) (Source: The Independent Health and Aged Care Pricing Authority).
Some maternity events (people giving birth in hospital and live babies born in hospital) are impacted by changes in the 11th Edition clinical coding standards, particularly place of birth and type of birth data. Therefore, this data may show variation due to the change in coding standards rather than a true increase.
The Primary Maternity Services Notice 2021 came into force on 29th November 2021, introducing changes to the terms and conditions on which maternity providers can claim for providing primary maternity services. This revokes the Primary Maternity Services Notice which came into effect on 1 July 2007 and its amendments.
There are underlying changes to the way some data are now captured (such as smoking status or breastfeeding and Well child referral). Also some metrics are no longer collected (such as height and weight at registration, which impacts on BMI calculation). It is important to consider these changes when comparing claims data pre and post November 2021.

At URL provided, under 'Babies' heading, select 'Birthweight by demographics for selected year' and download all data.

The National Maternity Collection collates data from three different sources to provide statistical, demographic and clinical information about people giving birth and live-born babies in New Zealand.
Data for the web tool was extracted from publicly funded maternity events recorded in Te Whatu Ora - Health New Zealand's National Maternity Collection on 17 September 2025.

To provide annual health statistics about people giving birth, their pregnancy and childbirth experience and the characteristics of live-born babies in New Zealand.

Population data for rate calculations was provided by Stats NZ.