A gene linked to premature births has been discovered by scientists in the US and Finland.
The researchers hope their study, published in PLoS Genetics, could eventually lead to a test for women at risk of a pre-term birth.
In the UK, one in 10 babies are born before the 37th week of pregnancy, with potential problems for their health.
The Royal College of Obstetricians and Gynaecologists said it would help to identify a percentage of those at risk.
The international team of researchers looked to human evolution in their hunt for genes linked to premature births.
In comparison to other primates and mammals, humans have relatively large heads and narrow birth canals.
Researchers at Vanderbilt University, Washington University and the University of Helsinki, believed there must have been an evolutionary pressure to “adapt and shift the time of birth” to produce a smaller baby.
They looked for DNA which showed evidence of “accelerated evolution” – genes which have mutated more in humans than in other primates.
They identified 150 genes.
In a separate study, a team at Washington State University believe they have identified why eggs are produced which result in miscarriage and birth defects.