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The total fertility rate (TFR) represents the number of children a woman would have during her lifetime if she were to experience current age-specific fertility rates at each stage of her reproductive life. Measures of the fertility of Indigenous females account for only part of the impact of births on measures of the growth of the Indigenous population. This is because the Indigenous TFR is based on the Indigenous status of the mother, and about one-third of Indigenous babies have an Indigenous father and non-Indigenous mother. In addition, the fertility rate of Indigenous females is likely to be underestimated because the Indigenous status of the mother is not always recorded in birth registrations that are used to calculate fertility rates. The TFR for 2006 was derived using the numbers of births registered to Indigenous mothers in 2006 and the 30 June 2006 preliminary estimated resident population of Aboriginal and Torres Strait Islander females.
In 2006, the TFR for Indigenous females was estimated to be 2.1 babies, compared with 1.8 babies for all Australian females. Indigenous TFRs vary across the states and territories. The highest Indigenous TFR in 2006 occurred in South Australia (2.5 babies per female), followed by the Northern Territory (2.4) and Western Australia (2.3) (ABS 2007a).
High fertility at younger ages contributes to the relatively high fertility of Indigenous females. Teenage births (i.e. births to females less than 20 years of age) are more common among Indigenous than non-Indigenous females. In 2006, the teenage birth rate for Indigenous females (69 babies per 1,000 females) was more than five times the teenage birth rate for non-Indigenous females (13 babies per 1,000 females). The peak age group for births to Indigenous females in 2006 was 20-24 years (125 babies per 1,000), followed by women aged 25-29 years (110 babies per 1,000 females). In contrast, the peak age group for births to non-Indigenous females was 30-34 years (120 babies per 1,000 females) (graph 6.3) (ABS 2007a).
The age of the mother can affect the development of the foetus, with the risk of foetal complications being higher for pregnancies that occur in the teenage years or among women over the age of about 35 years. Maternal age is also associated with perinatal health, with adverse outcomes more likely among younger and older mothers (Laws et al 2006a). The median age of Indigenous mothers in the period 2001-2004 was 25 years, some five years lower than the median age of non-Indigenous mothers (30 years) (AIHW: Leeds et al 2007).
In the period 2001-2004, approximately 23% of Indigenous females who gave birth were aged less than 20 years, compared with 4% of non-Indigenous females. The jurisdiction with the largest proportion of Indigenous females aged less than 20 years who gave birth during this period was the Northern Territory (29%), followed by Western Australia (24%), Victoria (22%) and South Australia (22%). The corresponding proportions for non-Indigenous females were 5% in the Northern Territory, 5% in Western Australia, 3% in Victoria and 5% in South Australia. Around 7% of Indigenous females who gave birth in the period 2001-2004 were aged 35 years or over compared with 19% of non-Indigenous females (table 6.4).
Risk factors during pregnancy
Smoking and alcohol use during pregnancy are both major risk factors for poor perinatal and child health.
Smoking during pregnancy increases the risk of complications and is associated with poorer perinatal outcomes, such as low birthweight, preterm birth and perinatal death (Graham et al 2007). Maternal factors that have been found to be associated with smoking during pregnancy include maternal age, marital status, socioeconomic status and number of children (Ventura et al 2003; Kahn et al 2002).
The National Perinatal Data Collection (NPDC) contains data on smoking during pregnancy from New South Wales, Western Australia, South Australia, the Australian Capital Territory and the Northern Territory for the period 2001-2004. During this period, half (51%) of Indigenous females in these states and territories reported smoking during pregnancy. Indigenous mothers were around three times as likely to smoke during pregnancy as non-Indigenous mothers ( Laws et al 2006b).
Excessive alcohol intake during pregnancy is associated with an increased risk of alcohol withdrawal symptoms in the baby, Foetal Alcohol Syndrome, and perinatal mortality (Walker, Rosenberg & Balaban-Gil 1999 in Zubrick et al 2004). In the 2001-02 WAACHS, the mothers of an estimated 23% of Aboriginal children in Western Australia reported that they had consumed alcohol during pregnancy (Zubrick et al 2004).
Maternal mortality is defined as the death of a woman while pregnant or within 42 days of the termination of pregnancy, irrespective of the duration and the site of the pregnancy, from any cause related to or aggravated by the pregnancy or its management, but not from accidental or incidental causes (Sullivan & King 2006). For the period 2000-2002 there were 13 maternal deaths of Aboriginal and Torres Strait Islander females (Sullivan & King 2006). For 2000-02, the maternal mortality rate for Indigenous females (45.9 per 100,000 females who gave birth) was five times the rate for non-Indigenous females (8.7 per 100,000 females who gave birth). The Indigenous maternal mortality rate is likely to be an underestimate because of incomplete ascertainment of Indigenous status in deaths data.