Physiology of uterine activity in pregnancy.

During the past few years enormous progress has been made in the understanding of the molecular mechanisms involved in parturition; however, the answer to the fundamental question of how labor is initiated remains elusive. This is a very important question because alterations in the timing of birth (preterm and post-term deliveries) are associated with much of perinatal morbidity and mortality. Currently available treatments for preterm labor are not clearly effective. Prevention of preterm delivery by home uterine monitoring has been proposed; however, the value of this technique has not been conclusively shown. A variety of substances have been implicated in the genesis of labor, including oxytocin, prostaglandins, cytokines, and endothelin. The role of infection in preterm labor has also been extensively studied, but it seems clear that a relatively small percentage of preterm labor is caused by infection. Attention has also focused on the role of estrogen and progesterone, and the possible uses of progesterone antagonists in the induction of labor. A better understanding of the relationship of intrauterine hypoxia and preterm delivery may also help us in establishing treatment and prevention strategies.