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National Indigenous Reform Agreement: PI 07—Proportion of babies born of low birthweight, 2017

Identifying and definitional attributes

Metadata item type:Help on this termIndicator
Indicator type:Help on this termIndicator
Short name:Help on this termPI 07—Proportion of babies born of low birthweight, 2017
METeOR identifier:Help on this term645396
Registration status:Help on this termIndigenous, Archived 06/06/2017
Description:Help on this term

The incidence of low birthweight among live born singleton babies by Indigenous status of mothers, and among live born singleton babies by Indigenous status of babies.

Rationale:Help on this term

Low birthweight is associated with increased risk of poor health and death during infancy and increased prevalence of a number of chronic diseases in adulthood. Low birthweight is a particular issue for Indigenous Australians.

Indicator set:Help on this termNational Indigenous Reform Agreement (2017) Indigenous, Archived 06/06/2017
Outcome area:Help on this termIndigenous children are born and remain healthy Indigenous, Endorsed 21/07/2010
Quality statement:Help on this termNational Indigenous Reform Agreement: PI 07-Proportion of babies born of low birthweight, 2015-16; Quality Statement Indigenous, Archived 07/02/2018

Collection and usage attributes

Computation description:Help on this term

Rates are calculated for Indigenous and non-Indigenous Australians.

Rate ratios and rate differences are calculated for comparisons between Indigenous and non-Indigenous Australians.

For variability bands:

Variability bands are to be calculated for rates (single year data and for total data for 3 years combined) using the standard method (see definition below).

For trends:

Percentage change and statistical significance of change is to be calculated (required for reporting of progress over time).

Presentation:

Number, rate per 100 babies (percentage), rate ratio, rate difference and variability bands.

Low birthweight is defined as less than 2,500 grams.

Excludes multiple births, stillbirths and births of less than 20 weeks gestation (where gestation is known).

Analysis by state/territory and remoteness is based on the usual residence of the mother.

Data exclude Australian non-residents, residents of external territories and records where state/territory of residence was not stated.

Definitions:

Standard method for variability band computation:

Rates derived from administrative data counts are not subject to sampling error but may still be subject to natural random variation, especially for small counts. A 95% confidence interval for an estimate is a range of values which is very likely (95 times out of 100) to contain the true unknown value. Where the 95% confidence intervals of two estimates do not overlap it can be concluded that there is a statistically significant difference between the two estimates. This is the standard method used in Australian Institute of Health and Welfare (AIHW) publications for which formulas can be sourced from Breslow and Day (1987) in the publication ‘Statistical methods in cancer research’. Typically in the standard method, the observed rate is assumed to have natural variability in the numerator count (for example, deaths, hospital visits) but not in the population denominator count. Also, the rate is assumed to have been generated from a normal distribution ("Bell curve"). Random variation in the numerator count is assumed to be centred around the true value, that is, there is no systematic bias.

Computation:Help on this term

Rate: 100 x (Numerator ÷ Denominator).

Rate ratio: Indigenous rate divided by non-Indigenous rate.

Rate difference: Indigenous rate minus non-Indigenous rate.

Variability bands: to be calculated using the standard method for estimating 95% confidence intervals as follows:

Crude rate:

 Crude rate formula (NIRA PIs 2013)

Where CI = confidence interval

CR = crude rate (expressed as a percentage)

n=number of live born singleton babies.

Percentage change: Calculated by multiplying the average annual change over the period by the number of data points less 1. This is then divided by the rate for the first year in the series and multiplied by 100.

The average annual change in rates, rate ratios and rate differences are calculated using linear regression which uses the least squares method to calculate a straight line that best fits the data and returns an array that best describes the line. The simple linear regression line, Y = a + bX, ‘slope’ (b) estimate was used to determine the average annual change in the data over the period. The formula used to calculate the slope estimate and standard error of the slope in Microsoft Excel is:

LINEST: (known_y’s, known_x’s, true) entered as an array formula (Ctrl, Shift, Enter).

Statistical significance of change:  The 95% confidence intervals (CIs) for the standard error of the slope estimate (average annual change) are used to determine whether the apparent increases or decreases in the data are statistically significant at the p<0.05 level. The formula used to calculate the CIs for the standard error of the slope estimate is:

95% CI(x) = x ± 1.96 x SE(x)

where x is the average annual change (slope estimate). If the upper and lower 95% confidence intervals do not include zero, then it can be concluded that there is statistical evidence of an increasing or decreasing trend in the data over the study period.

Numerator:Help on this term

Number of low birthweight live born singleton babies.

Numerator data elements:Help on this term
Data Element / Data SetBirth—birth weight, total grams NNNN
Data Source
AIHW National Perinatal Data Collection (NPDC)
NMDS / DSS
Perinatal NMDS 2014-18
Guide for use

Data source type: Administrative by-product data


Data Element / Data SetBirth event—birth plurality, code N
Data Source
AIHW National Perinatal Data Collection (NPDC)
NMDS / DSS
Perinatal NMDS 2014-18
Guide for use

Data source type: Administrative by-product data


Data Element / Data SetBirth—birth status, code N
Data Source
AIHW National Perinatal Data Collection (NPDC)
NMDS / DSS
Perinatal NMDS 2014-18
Guide for use

Data source type: Administrative by-product data


Denominator:Help on this term

Number of live-born singleton infants

Denominator data elements:Help on this term
Data Element / Data SetBirth event—birth plurality, code N
Data Source
AIHW National Perinatal Data Collection (NPDC)
NMDS / DSS
Perinatal NMDS 2014-18
Guide for use

Data source type: Administrative by-product data


Data Element / Data SetBirth—birth status, code N
Data Source
AIHW National Perinatal Data Collection (NPDC)
NMDS / DSS
Perinatal NMDS 2014-18
Guide for use

Data source type: Administrative by-product data


Data Element / Data SetProduct of conception—gestational age, completed weeks N[N]
Data Source
AIHW National Perinatal Data Collection (NPDC)
NMDS / DSS
Perinatal NMDS 2014-18
Guide for use

Data source type: Administrative by-product data


Disaggregation:Help on this term

Indigenous status of the mother

Current period—(2012–2014):

For Indigenous and non-Indigenous (number, rate, rate ratio, rate difference and variability bands):

  • Total and state/territory: by Indigenous status of the mother.
  • Total by remoteness area: by Indigenous status of the mother.

Time series—2007, 2008, 2009, 2010, 2011, 2012, 2013  (the data for these years have been previously supplied), 2014 (required for 2017 reporting):

For Indigenous and non-Indigenous (number, rate, rate ratio, rate difference and variability bands):

  • Total and state/territory: by Indigenous status of the mother.
  • Total by remoteness area (from 2012 onwards): by Indigenous status of the mother.

Indigenous status of the baby

Current period—(2013–2014):

For Indigenous and non-Indigenous (number, rate, rate ratio, rate difference and variability bands):

  • Total and state/territory: by Indigenous status of the baby.
  • Total by remoteness area: by Indigenous status of the baby.

Time series—2011, 2012, 2013 (the data for these years have been previously supplied), 2014 (required for 2017 reporting).

For Indigenous and non-Indigenous (number, rate, rate ratio, rate difference and variability bands):

  • Total and state/territory: by Indigenous status of the baby.
  • Total by remoteness area: by Indigenous status of the baby.

Indigenous status of the baby cross-tabulated by the Indigenous status of the mother

Current period only—(2013–2014):

For Indigenous and non-Indigenous (number, rate, rate ratio and rate difference):

  • Total and state/territory: by Indigenous status of the baby and of the mother.
Disaggregation data elements:Help on this term
Data Element / Data SetPerson—area of usual residence, statistical area level 2 (SA2) code (ASGS 2011) N(9)
Data Source
AIHW National Perinatal Data Collection (NPDC)
NMDS / DSS
Perinatal NMDS 2014-18
Guide for use

Data source type: Administrative by-product data

Used for disaggregation by state/territory and remoteness area. Classifications for remoteness area are based on Australian Standard Geographical Classification (ASGC) prior to 2012 and Australian Statistical Geography Standard (ASGS)  from 2012.


Data Element / Data SetPerson—Indigenous status, code N
Data Source
AIHW National Perinatal Data Collection (NPDC)
NMDS / DSS
Perinatal NMDS 2014-18
Guide for use

Data source type: Administrative by-product data.


Comments:Help on this term

Most recent data available for 2017 report (2015–16 reporting cycle) is 2014.

Aggregated data for a 3-year period (2012 to 2014) will be reported for the current reporting period (where data are available).

Single year data (2007, 2008, 2009, 2010, 2011, 2012, 2013 and 2014) will be reported for time series, noting that previously supplied data will be used unless a resupply is provided.

Information is included in the National Perinatal Data Collection (NPDC) for all live births and stillbirths of at least 400 grams birthweight or at least 20 weeks gestation.

Until 2011, the NPDC only included information on the Indigenous status of the mother. From 2011, the NPDC included information on the Indigenous status of the baby for selected jurisdictions—NSW, Vic, Qld, Tas, the ACT and the NT. The mandatory collection of this data item began from July 2012 following its inclusion in the Perinatal National Minimum Data Set (NMDS). National data based on the NMDS data item are therefore available for the latter 6 months of 2012, and 2013 is the first full calendar year for which nationally standardised data on the Indigenous status of babies are available.

Disaggregation by Indigenous status is recommended to be reported using 3-year combined data for the current reporting period due to the relatively small number of low birthweight babies born to Indigenous mothers each year. Single year data are to be reported for time series.

To report trends, the body assessing progress over time may separately request percentage change and statistical significance testing for this indicator directly from the data provider (AIHW).

For the 2017 report (2015–16 reporting cycle), a contextual table that shows data on low birthweight by the Indigenous status of the baby stratified by the Indigenous status of the mother is included for the first time. For this report, 2 full years of nationally standardised data are available (2013 and 2014 combined). For future reporting cycles, 3 years of data will be combined.

Variability bands accompanying perinatal data should be used where there are at least 3 full calendar years of data available for the purposes of comparisons over time and for national estimates at a point in time for Indigenous/non-Indigenous comparisons.

Baseline year for National Indigenous Reform Agreement (NIRA) target (Halve the gap in mortality rates for Indigenous children under 5 within a decade) is 2008; baseline year for this indicator is 2007; target year is 2018.

Representational attributes

Representation class:Help on this termPercentage
Data type:Help on this termReal
Unit of measure:Help on this termPerson
Format:Help on this term

N[N].N

Indicator conceptual framework

Framework and dimensions:Help on this termHealth Conditions

Data source attributes

Data sources:Help on this term
Data SourceAIHW National Perinatal Data Collection (NPDC)
Frequency
Calendar years ending 31 December each year
Data custodian

Australian Institute of Health and Welfare


Accountability attributes

Reporting requirements:Help on this term

National Indigenous Reform Agreement.

Organisation responsible for providing data:Help on this term

Australian Institute of Health and Welfare.

Further data development / collection required:Help on this term

Specification: Long-term.

A data item for Indigenous status of the baby was added to the Perinatal National Minimum Data Set (NMDS) for collection from July 2012 onwards.

Source and reference attributes

Steward:Help on this termNational Indigenous Reform Agreement Performance Information Management Group
Reference documents:Help on this term

Breslow NE & Day NE 1987. Statistical methods in cancer research. Lyon: International Agency for Research on Cancer.

Relational attributes

Related metadata references:Help on this term

See also National Healthcare Agreement: PI 01-Proportion of babies born of low birth weight, 2015 Health, Superseded 08/07/2016

Has been superseded by National Indigenous Reform Agreement: PI 07-Proportion of babies born of low birthweight, 2018 Indigenous, Archived 31/07/2018

Supersedes National Indigenous Reform Agreement: PI 07—Proportion of babies born of low birthweight, 2016 Indigenous, Archived 01/07/2016

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