Preterm births in Iceland 1997-2016: Preterm birth rates by gestational age groups and type of preterm birth.

Background: The frequency of preterm births has been increasing globally, mainly due to a rise in iatrogenic late preterm births. The aim of this study was to assess the prevalence of preterm births in Iceland during 1997-2016 by type of preterm birth.

Methods: This study included all live births in Iceland during 1997-2016 identified from the Icelandic Medical Birth Registry.