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).

The figure shows a grouped bar chart comparing the distribution of babies by gestational age in 2009 and 2019.

Over time, the proportion of babies born between 20 and 36 weeks remained steady (8.2% in 2009 compared with 8.6% in 2019), while the proportion born between 37 and 39 weeks increased (for example, babies born at 38 weeks increased from 19% in 2009 to 23% in 2019) and the proportion born from 40 weeks onwards decreased (for example, babies born at 40 weeks decreased from 27% in 2009 to 21% in 2019).

The figure shows a bar chart of the proportion of babies by gestational age by a range of topics for 2019 and a line graph of topic trends between 2009 and 2019. In 2019, 8.6% or 25,933 babies were born pre-term.

The vast majority of 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 (8.6%) 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 (12.8%) than babies born to mothers who had not smoked (8.0%).

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 98% for other multiples).

For more information on gestational age see National Perinatal Data Collection annual update data tables 3.5 and 3.6.