Premature birth is a leading cause of infant death and disability. Babies born before 37 weeks are considered premature. They have 120-times greater risk of death than a baby born full term.
Researchers discovered the immune systems of some women are more sensitive to infections and inflammation. These immune system chemicals fight infections, but they could also bring on contractions or premature labor.
Other possible causes of premature birth include stress, bleeding, and stretching of the uterus caused by multiple fetuses.
The study was done by the National Institutes of Health.