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Births and pregnancy outcome

Births and pregnancy outcome

In 2010, there were 16,129 births registered in Australia with one or both parents identified as Indigenous (4% of all births registered) [1], but this figure probably underestimates the true number slightly as Indigenous status is not always identified, and there may be a lag in birth registrations. The ABS estimated that 96% of Indigenous births in 2002-2006 were correctly identified as such [2]. Completeness of identification varied across the country, with only Vic, Qld, WA, SA and the NT having levels above 90%.

In 2010, both parents identified as Indigenous in 32% of Indigenous registered births [1]. Only the mother identified as Indigenous in 42% of these births (including births where paternity was not acknowledged and those where the father’s Indigenous status was unknown), and only the father identified as Indigenous in 27% (including births where the mother’s Indigenous status was unknown).

Age of mothers

In 2010, Indigenous women had more babies and had them at younger ages than did non-Indigenous women – teenagers had one-fifth (20%) of the babies born to Indigenous women, compared with only 4% of those born to all mothers [1]. The median age of Indigenous mothers was 24.6 years, compared with 30.7 years for all mothers. The highest birth rates (known technically as fertility rates) were for the 20-24 years age-group for Indigenous women and in the 30-34 years age-group for non-Indigenous women (Table 2). The fertility rate of teenage Indigenous women (76 babies per 1,000 women) was almost five times that of all teenage women (16 babies per 1,000).

Total fertility rates

In 2010, total fertility rates were 2,575 births per 1,000 Indigenous women and 1,886 per 1,000 for all women (Table 3) [3]. The highest total fertility rate for Indigenous women was for Qld (3,167 babies per 1,000 women), followed by WA (2,844 per 1,000) and SA (2,724 per 1,000).

Birthweights

The average birthweight of babies born to Indigenous mothers in 2008 was 3,196 grams, almost 200 grams less than the average for babies born to non-Indigenous mothers (3,385 grams) [4]. Babies born to Indigenous women in 2008 were twice as likely to be of low birthweight (LBW) (12.3%) than were those born to non-Indigenous women (5.9%) (Table 4). (LBW, defined as a birthweight of less than 2,500 grams, increases the risk of death in infancy and other health problems.) The low-birthweight proportions for babies born to Indigenous women were highest in SA (16.3%), WA (14.8%) and Vic (14.2%).

Risk factors for LBW include socioeconomic disadvantage, the size and age of the mother, the number of babies previously born, the mother’s nutritional status, illness during pregnancy, and duration of the pregnancy [5]. A mother’s alcohol consumption and use of tobacco and other drugs during pregnancy also impacts on the size of her baby.

Tobacco, in particular, has a major impact on birthweight. The mean birthweight of live babies born in 2001-2004 to Indigenous women who smoked was 3,037 grams, more than 250 grams lighter than those born to Indigenous women who did not smoke (3,290 grams) [6]. The comparable figures for live babies born to non-Indigenous women were 3,210 and 3,416 grams, respectively. The impact of tobacco smoking during pregnancy was seen also in the proportions of low birthweight liveborn babies – 16% and 10% respectively for Indigenous and non-Indigenous women who smoked during pregnancy, and 10% and 5% for those who didn’t.

The 2000-2001 Western Australian Aboriginal Child Health Survey (WAACHS) reported slightly higher average birthweights than the weights documented above – 3,110 grams for babies born to Indigenous mothers who used tobacco in pregnancy and 3,310 grams for those whose Indigenous mothers did not [7]. The lowest average birthweights reported in the WAACHS were for babies whose Indigenous mothers used marijuana with tobacco (3,000 grams) or marijuana with both tobacco and alcohol (2,940 grams).

References

1. Australian Bureau of Statistics (2011) Births, Australia, 2010. Canberra: Australian Bureau of Statistics
2. Australian Bureau of Statistics (2007) Births, Australia, 2006. Canberra: Australian Bureau of Statistics
3. Australian Bureau of Statistics (2011) Births, Australia, 2010: Table 10: Births of Australian Aboriginal and Torres Strait Islander peoples, summary, states and territories - 2005 to 2010 [data cube]. Retrieved 25 October 2011 from http://www.abs.gov.au/AUSSTATS/subscriber.nsf/log?openagent&33010do010_2010.xls&3301.0&Data%20Cubes&2DE7BE6B56F2ED80CA25793300168023&0&2010&25.10.2011&Latest
4. Laws PJ, Li Z, Sullivan EA (2010) Australia's mothers and babies 2008. Canberra: Australian Institute of Health and Welfare
5. Ashdown-Lambert JR (2005) A review of low birth weight: predictors, precursors and morbidity outcomes. Journal of the Royal Society for the Promotion of Health; 125(2): 76-83
6. Leeds K, Gourley M, Laws P, Zhang J, Al-Yaman F, Sullivan EA (2007) Indigenous mothers and their babies, Australia 2001-2004. Canberra: Australian Institute of Health and Welfare
7. Zubrick SR, Lawrence DM, Silburn SR, Blair E, Milroy H, Wilkes T, Eades S, D'Antoine H, Read AW, Ishiguchi P, Doyle S (2004) The health of Aboriginal children and young people. Perth: Telethon Institute for Child Health Research