3. Low birthweight
Why are low birthweight rates important?
Babies who are born with low birthweight are at greater risk of poor health, disability and death than other babies.
Birthweight is a key indicator of infant health and a principal determinant of a baby’s chance of survival and good health. A baby may be small due to being born early (pre-term) or may be small for gestational age (suggesting possible intrauterine growth restriction).
Low birthweight is a risk factor for neurological and physical disabilities, with the risk of adverse outcomes increasing with decreasing birthweight (Goldenberg & Culhane 2007). The health effects of low birthweight can continue into adulthood. Research has found an increased risk of Type 2 diabetes, high blood pressure as well as metabolic and cardiovascular diseases (Phillips 2006; Verrips & Van der Pal 2014).
Factors that contribute to low birthweight include extremes of maternal age, illness during pregnancy, low socioeconomic position, multiple pregnancy, maternal history of spontaneous abortion, harmful behaviours such as smoking or excessive alcohol consumption, poor nutrition during pregnancy and poor antenatal care (AIHW 2015; AIHW 2014; Goldenberg & Culhane 2007). A number of these risk factors are modifiable and amenable to intervention.
Recent studies have demonstrated associations between aggressions suffered during individual phases of somatic development and amplified risk of chronic diseases throughout life, such as obesity, diabetes and cardiovascular diseases (Silveira, Portella, Goldani, Barbieri 2007).
National Core Maternity Indicator 10 reports on the proportion of babies born at or after 40 weeks gestation who weighed less than 2,750 grams at birth. This may be used alongside this Children’s Headline Indicator on low birthweight to provide a picture of factors affecting low birthweight (noting that the two cut–off weights are slightly different).
More data on birthweight can be found on the Perinatal data portal, which reports on 3 birthweight groups: low (less than 2,500 grams), normal (2,500 to 4,449 grams) and high (4,500 grams and over).
Does low birthweight vary across population groups?
According to the 2015 AIHW National Perinatal Data Collection, 6.5% of liveborn babies in Australia were of low birthweight. Baby girls were more likely to be of low birthweight than boys (7.0% compared with 6.0%). Twice as many babies of Indigenous mothers were of low birthweight (11.9%) compared to babies of non-Indigenous mothers (6.2%). The proportion of low birthweight babies born to overseas-born mothers was marginally lower than the rate for Australian-born mothers (6.5% and 6.4% respectively). Babies born to mothers in Remote and very remote areas were more likely to be of low birthweight as those born to mothers in Major cities (8.6% compared with 6.4%). Babies born to mothers in the lowest socioeconomic areas were more likely to be of low birthweight as those born to mothers in the highest socioeconomic areas (7.6% compared with 5.5%).
Has there been a change over time?
There has been little change in the proportion of low birthweight babies over the 10 years to 2015 which remained between 6.1% and 6.5%. The rate for Indigenous babies also remained fairly constant, ranging between 11.8% and 12.6%. Similarly, the rate of low birthweight babies among overseas-born mothers remained relatively constant, ranging between 5.9% and 6.4%. Between 2006 and 2015, the low birthweight rate for mothers living in Remote and very remote areas ranged from 7.8% to 9.0%. The 2015 value of 8.6% is in the middle of this range. Between 2012 and 2015, the proportion of low birthweight babies born to mothers living in the lowest socioeconomic areas increased slightly (from 7.4% to 7.6%). The proportion of low birthweight babies born to mothers from highest socioeconomic areas showed similar change between 2012 and 2015, increasing slightly from 5.3% to 5.5%.
Low birthweight is defined as less than 2500 grams for the purpose of this indicator (AIHW 2014a).
The low birthweight indicator reported here does not currently distinguish between pre-term babies who are appropriate weight for gestational age and full-term babies who are small for gestational age.
The proportion of low birthweights for babies born in the ACT to Indigenous mothers has not been reported due to a low overall number of births recorded for Indigenous mothers in the ACT in that year.
- Australian Institute of Health and Welfare (AIHW) 2015. Australia's mothers and babies 2013 —in brief. Perinatal statistics series no. 31. Cat. no. PER 72. Canberra: AIHW.
- AIHW 2014. Birthweight of babies born to Indigenous mothers. Cat. no. IHW 138. Canberra: AIHW.
- Goldenberg RL & Culhane JF 2007. Low birthweight in the United States. American Journal of Clinical Nutrition 85:584S–90S.
- Phillips D 2006. Birth weight and adulthood disease and the controversies. Fetal and Maternal Medicine Review 17(3):205–27.
- Silveira, PP, Portella, AK, Goldani, MZ & Barbieri MA (2007) Developmental origins of health and disease (DOHaD). Journal of Pediatric (Rio J) 83(6): 494-504.
- Verrips GE & Van der Pal S 2014. Low birth weight babies. Encyclopedia of Quality of Life and Well-Being Research 3712-3715.