Birthweight
Birthweight is the first weight of the baby obtained after birth. Birthweight is reported in 3 categories: low birthweight (birthweight less than 2,500 grams), healthy birthweight (birthweight between 2,500 and 4,499 grams) and high birthweight (birthweight of 4,500 grams or more). For more information on birthweight, see Birthweight in Australia's mothers and babies.
Babies with birthweights outside the healthy range are at greater risk of illness, poor development, perinatal death and poorer health in adulthood (AIHW 2023).
Reviews have provided international evidence that COVID-19 infection during pregnancy increases the rate of low birthweight (New South Wales Health 2021; Smith et al. 2023; Wei et al. 2021).
In Australia, there was no increase in the rate of babies who were low birthweight (AIHW 2023). This may be due to Australia’s relatively low infection rate during this time.
Figure 27 presents data on birthweight.
Figure 27: Proportion of live births, by birthweight and state and territory of birth, 2015 to 2021
Line graph shows birthweight by state and territory of birth between 2015 and 2021.
Between 2015 and 2019, the proportion of liveborn babies who were of low birthweight has remained stable across Australia (from 6.5% in 2015 to 6.6% in 2019). Modelling showed that this was a small annual increase of 0.1 percentage points. The observed proportion of liveborn babies who were of low birthweight was 6.5% in 2020 and 6.3% in 2021, which was lower than the predicted proportions based on the modelling (6.8% in 2020 and 6.8% in 2021). This equated to around 2,390 more babies born at a healthy birthweight than predicted in 2020 and 2021 combined.
Data for modelling exclude 'Not stated' data and therefore may not match the proportions presented in the data visualisation above. For more information on modelling the trend over time, see Methods.
Babies of mothers who lived in some geographical locations were more likely to be low birthweight. Explore the map below (Figure 28) to view data on the number and proportion of babies who were low birthweight by PHN, remoteness and SA3.
Figure 28: Proportion of low birthweight live births, by selected geography, 2017 to 2021
Map shows proportion of low birthweight births by selected geographies and years.
AIHW (Australian Institute of Health and Welfare) (2023) Australia’s mothers and babies, AIHW, Australian Government.
New South Wales Health (2021) Foetal and neonatal outcomes of COVID-19 in pregnancy, New South Wales Health website.
Smith ER, Oakley E, Grandner GW, Ferguson K, Farooq F, Afshar Y, Ahlberg M, Ahmadzia H, Akelo V, Aldrovandi G, Tippett Barr BA, Bevilacqua E, Brandt JS, Broutet N, Fernández Buhigas I, Carrillo J, Clifton R, Conry J, Cosmi E, Crispi F, Crovetto F, Delgado-López C, Divakar H, Driscoll AJ, Favre G, Flaherman VJ, Gale C, Gil MM, Gottlieb SL, Gratacós E, Hernandez O, Jones S, Kalafat E, Khagayi S, Knight M, Kotloff K, Lanzone A, Le Doare K, Lees C, Litman E, Lokken EM, Laurita Longo V, Madhi SA, Magee LA, Martinez-Portilla RJ, McClure EM, Metz TD, Miller ES, Money D, Moungmaithong S, Mullins E, Nachega JB, Nunes MC, Onyango D, Panchaud A, Poon LC, Raiten D, Regan L, Rukundo G, Sahota D, Sakowicz A, Sanin-Blair J, Söderling J, Stephansson O, Temmerman M, Thorson A, Tolosa JE, Townson J, Valencia-Prado M, Visentin S, von Dadelszen P, Adams Waldorf K, Whitehead C, Yassa M and Tielsch JM (2023) ‘Adverse maternal, fetal, and newborn outcomes among pregnant women with SARS-CoV-2 infection: an individual participant data meta-analysis’, BMJ Glob Health, 8(1):9495, doi:10.1136/bmjgh-2022-009495.
Wei SQ, Bilodeau-Bertrand M, Liu S and Auger N (2021) ‘The impact of COVID-19 on pregnancy outcomes: a systematic review and meta-analysis’, CMAJ, 193(16):540-548, doi:10.1503/cmaj.202604.