Methods of cervical ripening and labor induction.

The overall rate of induction of labor in the United States in 1993 was 134 per 1,000 live births, or over 527,000 of the four million births that occur annually in the United States. Indications for labor induction include postdate pregnancy, premature rupture of membranes (PROM), and maternal medical complications, such as diabetes mellitus and pregnancy-induced hypertension. This article briefly reviews common indications for induction of labor and the importance of cervical ripening. It then addresses methods used to hasten cervical ripening and to induce labor, ranging from the more "natural" and noninvasive methods, such as nipple stimulation, to the newest commercially available formulation of prostaglandin. Methods well documented in the scientific literature, as well as those commonly used but less well studied, are included. Although one may argue about the "invasive" nature of these methods, they are addressed, in general, from the most natural methods to the latest pharmacologic methods, and they include the following: sexual intercourse, nipple/breast stimulation, herbal preparations, homeopathic solutions, castor oil, enemas, acupuncture, membrane sweeping or stripping, mechanical dilation (balloon catheters, laminaria, and synthetic osmotic dilators), amniotomy, and pharmacologic hormonal preparations (prostaglandin E2, oxytocin, misoprostol, mifepristone, and relaxin).