Specifications and notes for analysis

Data specifications

Table 6: Data Specifications for National Core Maternity Indicators
IndicatorMETEOR identifier
Indicator Set: National Core Maternity Indicators, 2023772600
Antenatal Indicators 
PI 01–Tobacco smoking in pregnancy for all females giving birth772603
PI 02–Antenatal care visits in the first trimester for all females giving birth772605
Labour and birth indicators 
Selected women 
PI 05–Induction of labour for selected females giving birth for the first time772611
PI 06–Caesarean section for selected females giving birth for the first time772613
PI 07–Non-instrumental vaginal birth for selected females giving birth for the first time772615
PI 08–Instrumental vaginal birth for selected females giving birth for the first time772617
All women 
PI 03–Episiotomy for females giving birth for the first time and giving birth vaginally772607
PI 09–General anaesthetic for females giving birth by caesarean section772619
PI 15–Females having their second birth vaginally whose first birth was by caesarean section772625
Birth outcome indicators 
PI 04–Apgar score of less than 7 at 5 minutes for births at or after term772609
PI 10–Small babies among births at or after 40 weeks gestation772621
PI 13–Third and fourth degree tears for vaginal births772623

Note: For reporting purposes, the terms 'females' and 'women' are used interchangeably.

Tobacco smoking during pregnancy

  • The smoking indicator has been calculated differently in reports of the National Core Maternity Indicators released from 2020. The current methodology provides a more accurate measure and aligns with the methodology used in the Australia’s mothers and babies reports, which also uses data from the National Perinatal Data Collection. Data for all years has been updated to reflect the improved methodology.
  • Smoking in the first 20 weeks of pregnancy for all women giving birth:
    • Calculation of the denominator includes the number of women who gave birth with a known smoking status in the first 20 weeks of pregnancy.
  • Smoking after the first 20 weeks of pregnancy for all women who gave birth and reported smoking during pregnancy:
    • Calculation of the numerator includes women who reported smoking in the first 20 weeks of pregnancy and after the first 20 weeks of pregnancy. Calculation of the denominator includes women who reported smoking in the first 20 weeks of pregnancy.

Antenatal care in the first trimester

  • The indicator 'Antenatal care visits in the first trimester for all women giving birth' has been calculated differently in reports of the National Core Maternity Indicators released from 2021. The current methodology provides a more accurate measure and aligns with the methodology used in the Australia’s mothers and babies reports, which also uses data from the National Perinatal Data Collection. Data for all years has been updated to reflect the improved methodology.
  • Calculation of the denominator includes women with a stated first antenatal visit in the valid range. The valid range for pregnancy duration at first antenatal visit is 3 to 46 weeks, and women with no antenatal care during pregnancy. Records with missing or invalid data for gestational age at first antenatal visit are excluded.

Vaginal birth after caesarean section

The indicator ‘Women having their second birth vaginally whose first birth was by caesarean section’ has been calculated differently in reports of the National Core Maternity Indicators released from 2021. The indicator was updated in 2021 to only include women whose second birth was a singleton birth. This methodology aligns with the indicator specification (METEOR 772625). Data for all years has been updated to reflect the updated methodology.

Selected women

  • In 2022, the selected women criteria were updated to revise the gestational age at birth range to between 37 and 40 completed weeks gestation (previously between 37 and 41 completed weeks gestation).
  • The following indicators report on selected women:
    • PI 05 Induction of labour for selected females giving birth for the first time.
    • PI 06 Caesarean section for selected females giving birth for the first time.
    • PI 07 Unassisted (non-instrumental) vaginal birth for selected females giving birth for the first time.
    • PI 08 Assisted (instrumental) vaginal birth for selected females giving birth for the first time.
  • Selected women may include women with other medical and obstetric complications.
  • These indicators have been calculated differently for this report than in reporting of the National Core Maternity Indicators released prior to 2022. This methodology aligns with the National Core Maternity Indicators, 2023 indicator specifications (METEOR 772600). Data for all years has been updated to reflect the updated methodology and may result in statistics that vary from what has previously been reported. Where necessary to prevent back-calculation of small numbers, consequential suppression has been applied as a result of this change.

n.a./n.p.

  • n.a. not available
  • n.p. not publishable – data were suppressed due to concerns about confidentiality or low reliability

Terminology

This report uses the terms 'woman' and 'women' to mean 'female' when referring to data collected in the National Perinatal Data Collection (NPDC) as these data sources are based on sex. Information on gender is not recorded in these data collections. 'Woman' and 'women' typically refers to groups of people aged 18 years and over, however in this report people who were pregnant or gave birth aged less than 18 are included.

The terms 'mother' and 'mothers' refers to females who were pregnant and within the scope of the data collection, for more information on the scope of the NPDC see the National Perinatal Data Collection details.

It is acknowledged that this report includes people who do not identify as women or mothers, and that individual parents and families may use different words to those used in this report. This may include women, transgender men, intersex people, non-binary and gender diverse people.

Notes for analysis by sub-populations

Data for all National Core Maternity Indicators (NCMI) are presented by three geographic boundaries:

  • state and territory of birth
  • Primary Health Network (PHN) of mother's usual residence
  • Statistical area (SA3) of mother's usual residence

and at the national level by:

  • hospital annual number of births
  • hospital sector
  • mother’s First Nations status.

Some indicators are disaggregated by other data groupings where relevant.

Notes for each sub-population analysis are provided in the following sections.

State and territory of birth

Births in 'Other territories' are included within their closest state.

Mother's First Nations status

  • First Nations women include those who identified as Aboriginal, Torres Strait Islander, or both Aboriginal and Torres Strait Islander origin. Non-Indigenous refers to women who have not identified as Aboriginal or Torres Strait Islander.
  • Excludes mothers for whom First Nations status is missing or not stated.
  • Data were directly age-standardised using the June 2001 Australian female estimated resident population aged 15–44 years.
  • Crude (non-age-standardised) percentages are also presented for this disaggregation.

Hospital sector

Includes births that occurred in a hospital only.

Hospital annual number of births

Includes births that occurred in a hospital only.

Primary Health Network (PHN) of mother's usual residence

  • PHN of mother's usual residence is presented using the boundaries released by the Department of Health in 2015 and 2017. Additional information: Primary Health Networks.
  • PHN is derived from Statistical Area Level 2 (SA2) of mother’s area of usual residence (ABS Australian Statistical Geography Standard Edition 2016).
  • Includes records where mother’s usual residence is an Australian state or territory (including 'Other territories').
  • Results for PHN are available from 2012 onwards.

Statistical Area Level 3 (SA3) of mother's usual residence

  • SA3 of mother's usual residence uses the Australian Bureau of Statistics, Australian Statistical Geography Standard (ASGS): Volume 1 – Main Structure and Greater Capital City Statistical Areas, July 2016, Statistical Area Level 3 (SA3); ABS cat. no. 1270.0.55.001. Available from: Statistical Area Level 3 (SA3).
  • SA3 was derived from SA2 of the ABS 2016 ASGS
  • Includes records where mother’s usual residence is an Australian state or territory (including 'Other territories').
  • Results for SA3 of mother's usual residence reported using a 3-year aggregate, 2019–2021. The 2019–2021 SA3 calculation has been reported using the ABS 2016 ASGS.

Mother's age at birth

Excludes mothers for whom age is missing or not stated.

Mother's smoking status during pregnancy

Excludes mothers for whom smoking status was not stated.

Whether labour was established

Excludes records where onset of established labour is not stated.

Sex of baby

Excludes records where sex of baby is not stated or not assigned.

Whether an episiotomy was performed

  • Data reported from 2004 to 2013, a combined laceration and episiotomy value could be recorded; from 2014 onwards, episiotomy could be recorded separately.
  • Excludes records where it is not stated whether an episiotomy was performed.

Mother's country of birth

  • Excludes records where mother's country of birth is not stated.
  • Data were mapped to the ABS Standard Classification of Countries (SACC), 2016 and reported at the minor group level of the classification.

Remoteness of mother's area of residence

  • Remoteness assigned using the ABS Australian Statistical Geography Standard (ASGS) remoteness structure applied to Statistical Area Level 2 (SA2) of mother’s usual residence.
  • Includes records where mother’s usual residence is an Australian state and/or territory (excluding 'Other territories').
  • Results for remoteness are only available from 2012.

Disadvantage quintile of mother's area of residence

  • Disadvantage quintile assigned using the ABS Socio-Economic Indexes for Areas Index Relative Socio-economic Disadvantage 2016 scores applied to Statistical Area Level 2 (SA2) of mother’s usual residence.
  • Only includes records where mother’s usual residence is an Australian state and/or territory (excluding 'Other territories').
  • Results for disadvantage quintile are only available from 2012.

Methods

Age-standardised percentages

  • Age-standardised percentages enable comparisons to be made between populations that have different age structures. Direct standardisation, in which the age-specific rates are multiplied by a constant population, was used in this report for data reported by mother’s First Nations status. This effectively removes the influence of the age structure on the summary rate. The report states where age-standardised percentages have been used.
  • All age-standardised percentages in this report have used the June 2001 Australian female estimated resident population aged 15–44 years as the standard population.
  • For more information on methods used to report NPDC data refer to: Australia’s mothers and babies – Methods.