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. 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).

Over time, the proportion of babies born between 20 and 36 weeks remained steady (8.3% in both 2010 and 2020), while the proportion born between 37 and 39 weeks increased (for example, babies born at 38 weeks increased from 19% in 2010 to 23% in 2020) and the proportion born from 40 weeks onwards decreased (for example, babies born at 40 weeks decreased from 26% in 2010 to 20% in 2020).

The data visualisation below presents data on the grouped gestational age of pre-term and post-term babies and the individual completed weeks for term babies, for 2010 and 2020.

The figure shows a grouped bar chart comparing the distribution of babies by gestational age in 2010 and 2020.

The data visualisation below presents data on the gestational age of babies, by selected maternal and baby characteristics, for 2020. Click the trend button to see how data has changed over an 11-year period (where available).

The figure shows a bar chart of the proportion of babies by gestational age by a range of topics for 2020 and a line graph of topic trends between 2009 and 2020. In 2020, 8.3% or 24,695 babies were born pre-term.

Most babies (91%) in Australia are born at term (37–41 weeks). This is similar across the states and territories and has been stable over time.

Almost 1 in 10 babies (8.3%) were born pre-term and of these the majority were born between 32 and 36 completed weeks.

Babies born to mothers who smoked at any point during pregnancy were more likely to be born pre-term (14%) than babies born to mothers who had not smoked (7.7%).

Most singleton babies were born at term (93%), while twins and babies of other multiple births were more likely to be born pre-term (65% for twins and 97% for other multiples).

For more information on gestational age see National Perinatal Data Collection annual update data table 3.5.