Researchers found that among 1,820 pregnant women, those with the greatest concerns about their pregnancy were nearly three times more likely than those with the least anxiety to deliver prematurely.

Stress during pregnancy has been linked to a higher risk of complications in some studies, though not all. And those that have identified a link have not suggested any simple solutions to the problem.

For the current study, researchers looked specifically at women's worries related to their pregnancy -- including anxiety over labor and delivery, and worries about early pregnancy problems like bleeding and nausea. The goal was to see whether the risk of preterm birth was influenced by the types of anxiety that obstetricians can fairly easily address.