What Causes Preterm Labor?
It is not known for certain what causes labor to start. Evidence suggests that there can be several causes, which may vary from case to case and often occur in combination. Hormones produced by the mother, placenta and fetus, as well as uterine changes, may contribute to the onset of labor, but the exact mechanisms are poorly understood. There are many reasons for PTL, however; in most cases, the exact cause is not known. Only about half the women who have preterm labor fall into any known risk group.
