Gestational age
Gestational age is the duration of pregnancy in completed weeks. The gestational age of a baby has important implications for their health, with poorer outcomes generally reported for those born early (AIHW 2023).
Gestational age is reported in 3 categories: pre-term (less than 37 weeks’ gestation), term (37 to 41 weeks) and post-term (42 weeks and over).
For more information on gestational age, see Gestational age in Australia's mothers and babies.
International research supports a link between COVID-19 infection during pregnancy and an increased risk of pre-term birth (Chinn et al. 2021; Neelam et al. 2022; Smith et al. 2022, 2023).
In Australia, the overall proportion of pre-term birth does not appear to have increased during the first 2 years of the COVID-19 pandemic (AIHW 2023), noting that Australia had a relatively low infection rate during this time.
In 2021, the National Preterm Birth Prevention Collaborative – which aims to support the adoption of evidence-based changes in clinical care to reduce preterm birth – expanded their program nationally.
Figure 25 presents data on gestational age.
Figure 25: Proportion of births, by gestational age and state and territory of birth, 2015 to 2021
Line graph shows births by gestational age by state and territory of birth between 2015 and 2021.
Between 2015 and 2019, the proportion of babies who were born pre-term remained relatively stable across Australia (from 8.7% in 2015 to 8.6% in 2019). Modelling showed that there was no annual change. The observed proportion of babies who were born pre-term was 8.3% in 2020 and 8.2% in 2021, which was lower than the predicted proportions based on the modelling (8.6% in 2020 and 8.6% in 2021). This equated to around 2,330 fewer babies born pre-term 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 born pre-term. Explore the map below (Figure 26) to view data on the number and proportion of babies who were born pre-term by PHN, remoteness and SA3.
Figure 26: Proportion of pre-term births, by selected geography, 2017 to 2021
Map shows proportion of pre-term births by selected geographies and years.
AIHW (Australian Institute of Health and Welfare) (2023) Australia’s mothers and babies, Cat. no. PER 101, Canberra: AIHW.
Chinn J, Sedighim S, Kirby KA, Hohmann S, Hameed AB, Jolley J and Nguyen NT (2021) ‘Characteristics and outcomes of women with COVID-19 giving birth at US academic centers during the COVID-19 pandemic’, JAMA Netw Open, 4(8):2120456, doi:10.1001/jamanetworkopen.2021.20456.
Neelam V, Reeves EL, Woodworth KR, Olsen EO, Reynolds MR, Rende J, Wingate H, Manning SE, Romitti P, Ojo KD, Silcox K, Barton J, Mobley E, Longcore ND, Sokale A, Lush M, Delgado-Lopez C, Diedhiou A, Mbotha D, Simon W, Reynolds B, Hamdan TS, Beauregard S, Ellis EM, Seo JY, Bennett A, Ellington S, Hall AJ, Azziz-Baumgartner E, Tong VT and Gilboa SM (2022) ‘Pregnancy and infant outcomes by trimester of SARS‐CoV‐2 infection in pregnancy–SET‐NET, 22 jurisdictions’, January 25, 2020–December 31, 2020’, Birth Defects Research, 115(2):145-159, doi:10.1002/bdr2.2081.
Smith LH, Dollinger CY, VanderWeele TJ, Wyszynski DF and Hernández-Díaz S (2022) ‘Timing and severity of COVID-19 during pregnancy and risk of preterm birth in the International Registry of Coronavirus Exposure in Pregnancy’, BMC Pregnancy and Childbirth 22(775), doi:10.1186/s12884-022-05101-3.
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.