APPENDIX 2 DIFFERENCES BETWEEN COLLECTIONS


BIRTH REGISTRATIONS COMPARED TO THE PERINATAL DATA COLLECTION

Birth registrations data in this publication are not the only births data available in Australia. The National Perinatal Statistics Unit of the Australian Institute of Health and Welfare (AIHW) also collects birth data from midwives and other health professionals who attend births. This data is published annually in Australia's Mothers and Babies.

As information from these two collections are from different sources, the statistics obtained vary. For example, the Perinatal Data Collection reported the occurrence of 280,100 live births in Australia in 2006 (the latest available data), 5.3% more than the 265,900 births registered in the same year.

Graph A1.1 shows the total number of live births in Australia by type of collection and recording basis from 1993 to 2008. Births from the Perinatal Data Collection are shown on a year of occurrence basis. Registered births from the ABS Birth Registrations collection are shown on both a year of registration and year of occurrence basis, which includes births that occurred in a particular year but may have been registered up to and including the year 2008. Prior to 1994, the Perinatal Data Collection showed fewer births than births registered. This position then reversed, with the gap between births reported in the two collections widening until 1999 (when there were 2.7% more births recorded in the Perinatal Data Collection than births registered). The size of the difference between the two collections decreased to 0.4% by 2004, and increased to 5.3% in 2006.

While difficult to explain the differences, the greater number of births in the Perinatal Data Collection may be due to improvements in quality and coverage, particularly with the introduction of a perinatal National Minimum Dataset (NMDS) in 1997 which developed national standards for the collection of perinatal statistics. The trend may also reflect the increasing likelihood over time of parent(s) to delay or fail to register the birth of a child.

The following analysis of differences between the collections is made on live births between the Perinatal Data Collection on a year of occurrence basis and the Birth Registrations collection on a year of registration basis.


Age of mother

Age of mother is a factor which contributes to differences between the two collections. In 2006, higher numbers of confinements were recorded in the Perinatal Data Collection than in the Birth Registrations Collection for mothers in all age groups. For mothers aged 19 years and under, there were 14.3% more confinements recorded in the Perinatal Data Collection than in the Birth Registrations Collection, while for mothers aged 20-24 years the difference was 9.9%.

A2.2 Confinements, Difference between collections by age of mother - 2006
	Perinatal Data Collection	Birth Registrations	Difference(a)
	no.	no.	%
19 years and under	11 977	10 474	14.3
20-24 years	40 461	36 811	9.9
25-29 years	73 504	69 263	6.1
30-34 years	92 163	88 211	4.5
35-39 years	49 802	47 388	5.1
40 years and over	9 462	8 887	6.5
Total(b)	277 436	261 550	6.1
(a) Positive figures denote more confinements recorded in the Perinatal Data Collection than the Birth Registrations collection.
(b) Includes age of mother not stated.

Births to Indigenous mothers

There are differences between Indigenous data from the Perinatal Data Collection and birth registrations data. In all years from 1998 to 2006 the number of births to Indigenous mothers as recorded in the Perinatal Data Collection exceeded registered births to Indigenous mothers. In 2006 there were 10,200 live births to Indigenous mothers recorded in the Perinatal Data Collection, 1,300 more than the number recorded in the Birth Registrations collection (8,800).

It is important to recognise that data concerning Indigenous status is affected by identification issues. Differences between the Perinatal Data Collection and birth registrations data may in part be due to undercoverage of registrations of Indigenous births or delays in the registration of Indigenous births. However, failure to determine Indigenous status may also affect the Perinatal Data Collection. As a result, caution should be used when interpreting Indigenous births data from either source. Paragraphs 30 to 35 of the Explanatory Notes provide further information about Indigenous births.

State and territory comparisons

While birth registration data provides information on state/territory of registration or state/territory of usual residence of mother, the Perinatal Data Collection only provides data on the state/territory in which the birth took place (that is, the state/territory of occurrence). The following table compares state/territory of usual residence from birth registrations to state/territory of occurrence from the Perinatal Data Collection. As a small number of births occur in a different state or territory to that of the mother's usual residence, there are some minor differences. For example, some women living in rural New South Wales close to the Australian Capital Territory have their babies in Canberra. As a consequence, the Australian Capital Territory has been excluded from the comparisons below.

In 2006, the Perinatal Data Collection recorded more births in New South Wales, Victoria, Queensland, South Australia, Western Australia and the Northern Territory, while the ABS birth registrations collection recorded more births in Tasmania.

A2.4 Live births, Type of collection by state/territory - 2006
	NSW	Vic.	Qld	SA	WA	Tas.	NT	Total(a)
Perinatal Data Collection (no.)	92 176	69 230	56 317	18 662	28 455	6 101	3 702	280 078
Birth Registrations (no.)	87 336	65 236	52 665	18 260	27 776	6 475	3 696	265 949
Difference (%)(b)	5.5	6.1	6.9	2.2	2.4	-5.8	0.2	5.3
(a) Includes Australian Capital Territory and Other Territories.
(b) Positive figures denote more births recorded in the Perinatal Data Collection than the Birth Registrations Collection.