Small babies among births at or after 40 weeks of gestation
Birthweight for gestational age is a key indicator of infant health that is used both as an outcome measure for health and wellbeing of the mother in pregnancy and a principal determinant of a baby’s chance of prospective survival, good health, development and wellbeing (DoH 2020). For more information, see Clinical commentary.
This indicator looks at small babies born at or after 40 weeks gestation with a birthweight less than 2,750 grams.
In 2021, 1.1% of babies born at or after term were classified as small.
The proportion of babies born at or after term who were classified as small:
- almost halved from 2.1% in 2004 to 1.1% in 2021
- was higher for babies born to mothers who reported smoking during pregnancy compared with mothers who did not (2.6% compared with 1.0% in 2021)
- was slightly higher for babies born to mothers living in areas of most disadvantage (1.4% in 2021) than other areas (1.0% in 2021).
The interactive data visualisation (Figure 14) presents data on small babies among births at or after 40 weeks gestation by selected maternal characteristics. Select the trend button to see how data have changed between 2004 and 2021.
Figure 14: Small babies among births at or after 40 weeks of gestation
Small babies among births at or after 40 weeks gestation, 2004 to 2021.
This chart shows the proportion of small babies among births at or after 40 weeks gestation, for the current data 2021 and trend data from 2004 to 2021. The proportion of small babies among births at or after 40 weeks gestation, for all Australia, showed a decreasing trend from 2.1% in 2004 to 1.1% in 2021.
Babies born at or after 40 completed weeks of gestation (280 or more days after the first day of the last menstrual period) with a birthweight less than 2,750 grams are considered small for gestational age and are likely to have been affected by intrauterine growth restriction (AIHW 2022). Poor fetal growth is associated with increased risks of fetal death and compromise in labour (Draper et al. 2017). Late fetal growth restriction may predispose the baby to hypertension and diabetes in adulthood (Flenady et al. 2018; Sharma et al. 2016).
Some babies whose intrauterine growth is normal are small, and female babies are normally smaller than male babies of the same gestational age. Use of sex-specific birthweight cut-off points would align this indicator more closely with growth restriction.
For this indicator, small babies at or after 40 weeks gestation is defined as a birthweight less than 2,750 grams; the definition of low birthweight (grams) may be different in other national or international reporting indicators.
AIHW (Australian Institute of Health and Welfare) (2022) Health of mothers and babies, AIHW, Australian Government, accessed 22 July 2022.
DoH (Department of Health) (2020) Clinical Practice Guidelines: Pregnancy Care 2020 Edition, DoH, Australian Government, accessed 6 June 2023.
Draper ES, Kurinczuk JJ and Kenyon S (Eds.) on behalf of MBRRACE-UK (2017) Perinatal Confidential Enquiry: Term, singleton, intrapartum stillbirth and intrapartum-related neonatal death, Department of Health Sciences, University of Leicester, Leicester, accessed 6 June 2023.
Flenady V, Wojiezek AM and Middleton P (2018) ‘Stillbirths: recall to action in high-income countries’, Lancet, 387(10019):691–702, doi:10.1016/S0140-6736(15)01020-X.
Sharma D, Shastri S and Sharma P (2016) ‘Intrauterine growth restriction: antenatal and postnatal aspects’, Clinical Medicine Insights: Pediatrics, 10:67–83, doi:10.4137/CMPed.S40070.