Chapter 44 Perinatal mortality, birth asphyxia and cerebral palsy
Background facts for live-born babies
• In 2007, 92.1% of live-born babies had a birthweight in the range of 2500–4499 g. The average birthweight of live-born babies in Australia in 2007 was 3374 g. For singletons, the mean gestational age was 38.9 weeks, compared with 35.3 weeks for twins and 31.3 weeks for triplets.
• 8.1% were preterm (<37 weeks gestation), compared with 7.3% in 1997. The mean gestational age for all preterm births was 33.2 weeks. 13.7% of babies of Aboriginal and Torres Strait Islander mothers were born preterm.
• 6.2% of live-born babies were of low birthweight (<2500 g). A baby may be small due to being born early (preterm), or may be small for its gestational age (intrauterine growth restriction). Low birthweight babies have a greater risk of poor health and dying, require a longer period of hospitalisation after birth, and are more likely to develop significant disabilities. The proportion of low birthweight in live-born babies of Aboriginal and Torres Strait Islander mothers was 12.5%, twice that of babies of non-Indigenous mothers (5.9%).
Definitions
• Intrauterine fetal death (IUFD). This is death of a fetus in utero after 20 weeks gestation or at birth weighing at least 400 g.
• Intrapartum death. This is fetal death during labour. If a baby is born without signs of life, but also without maceration, there is a strong presumption that death occurred during labour. There are exceptions in both directions, which require judgment on the timing of death in relation to the presumed onset of labour.
• Stillbirth (fetal death). This is the death of a fetus before delivery when the gestation has reached at least 20 weeks or the weight is over 400 g. This Australian definition differs from the World Health Organization definition, which requires the stillborn infant to weigh at least 1000 g or to have reached at least 28 weeks gestation. Therefore, caution is required in comparing international rates. The stillbirth rate is 7.4 per 1000 births in Australia. Low birthweight occurred in 79% of stillborn babies, with 28% of these unexplained. The mean gestational age of stillborn babies was 27.4 weeks in 2007 compared with 38.9 weeks for live-born babies. Preterm birth occurred in 80.8% of stillborn babies, compared with 7.6% of live-born babies.
• Neonatal death. This is the death of a live-born baby of at least 20 weeks gestation or 400 g in weight within 28 days of delivery. In comparison, the WHO definition is the death of an infant of at least 1000 g or 28 weeks gestation that occurs within 7 days of birth. In 2007, the neonatal death rate (NDR) was 2.9 per 1000 live births. Congenital abnormality occurred in a higher proportion of neonatal deaths (31.3%) than fetal deaths (20.8%). Among neonatal deaths, congenital abnormalities accounted for 67.7% of babies born at 32–36 weeks and 37.3% of babies at 37 weeks or more. The second most common cause of fetal deaths was maternal conditions (18.1%) and the proportion was highest among babies of 20–27 weeks (22.4%). Spontaneous preterm birth was a common cause of neonatal death for babies born at 20–27 and 28–31 weeks.
