Methods of Cervical Ripening and Induction
There are various methods used to induce labor. The oldest and most common medication used for IOL is IV oxytocin (Pitocin). Other methods to help ripen (soften, thin, and dilate) the cervix and induce labor include: membrane stripping, amniotomy, nipple stimulation, prostaglandin E analogs (Cervidil and Cytotec ®), and mechanical cervical catheters (Cook or Foley ®).
Mechanical cervical ripening methods
Stripping (or sweeping) of the fetal membranes occurs by the examiner inserting a finger beyond the inner cervical canal and then rotating the finger around to separate the fetal membranes from the cervical wall.
Foley or Cook ® ballon catheter is inserted within the cervical canal past the inner (deeper) cervix and then the balloon is filled with an infusion of saline. With time this balloon helps mechanically dilate the cervix.
Both these mechanical methods work by causing the release of prostaglandins around the tissues surrounding the membranes and cervix. Catheters gradualy dilate the cervix with minimal discomfort to the patient.
Cervical ripening medications
Prostoglandin E1 (prepedil and cervidil) and Prostoglandin E2 (misoprostal/ Cytotec) work by breaking down collagen bundles and increasing the water content of the cervical tissue. These alterations help the cervix become softer and thinner and helps the uterus contract.
Oxytocin (Pitocin) is a naturally occurring hormone that is produced in the brain. Synthetic oxytocin remains identical to the natural occurring hormone in the human body and is among the most powerful uterine contraction agents known. It is a proven induction method (Kelly and Tan, 2001).
Amniotomy (breaking the bag of water) is sometimes used to induce labor or help continue labor. There is no evidence to support use of amniotomy used alone for IOL, especially if the cervix is unfavorable (not very dilated or effaced). It may shorten labor when used with IV Oxytocin (Pitocin) or when a woman is already in active labor (ACOG, 2009).
Nipple stimulation helps release natural oxytocin and causes uterine contractions. In women with favorable cervices, nipple stimulation appears to help initiate labor within 72 hrs compared to control groups as examined in a Cochrane Review (Kavanagh et al., 2005)