Spontaneous and induced cervical ripening. Natural dilation and effacement process and current cervical ripening techniques.

During gestation, the cervix forms a tight sphincter to ensure the integrity of the pregnancy. Toward the end of the pregnancy, hormone-mediated biochemical changes cause the cervix to ripen and become softer and more pliable to allow passage of the fetus. Failure of the cervix to ripen may result in delayed onset of labor and a prolonged and complicated course, especially if labor is artificially induced. Attempts to induce cervical ripening have involved the use of mechanical methods, estrogen and estrogen precursors, relaxin and prostaglandins. The ideal ripening agent is simple and noninvasive, effective within 24 hours, does not compromise mother or fetus and does not stimulate labor (during the ripening process).