What is preterm birth?

1. What is preterm birth?

The length of a pregnancy is measured in weeks of gestation from the mother’s last period. A full-term pregnancy lasts for approximately 40 weeks of gestation. A preterm or premature birth is where a baby is born before 37 completed weeks of gestation. Although most preterm babies are born just a few weeks early, some are born and survive as early as 23 weeks, which is just over half way through a full-term pregnancy.

The earlier a baby is born, the more medical care they need around the time of birth. Preterm births are categorised into groups depending on the week of gestation in which they are born. Select each section of the table to find out how they are grouped and the number of children who are affected.

Completed Weeks of Gestation
22-27 28-31 32-36 37-41
22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41
Extremely Preterm
Very Preterm
Moderate & Late