Increases in spontaneous and medically induced preterm births have made equal contributions to a rise in preterm births, suggest researchers.
The team from the University of Edinburgh said previous research had thrown up conflicting causes for the global rise in preterm birth.
They looked at Scottish data on 90,000 preterm births over the past 25 years.
They found the absolute increase in the rate of preterm births was similar in each group – 4.24 per 1,000 births for medically induced compared with 4.71 for spontaneous.
Writing in the online journal PLoS Medicine, the authors said: “In our population, increases in spontaneous and medically induced preterm births have made equal contributions to the rising rate of preterm birth.
“Despite improvements in related perinatal mortality, preterm birth remains a major obstetric and neonatal problem, and its frequency is increasing,” they said.
RCM general secretary professor Cathy Warwick said: “There needs to be a close examination of reasons for increased medical interventions during labour and the pre-term induction of mothers. There also needs to be a measured consideration of the risks and benefits of delivering babies pre-term.”