Cervical effacement or cervical ripening refers to the thinning and shortening of the cervix. This process occurs during labor to prepare the cervix for dilation to allow the fetus to pass through the vagina. While this is a normal, physiological process that occurs at the later end of pregnancy, it can also be induced through medications and procedures.

During gestation, the cervix maintains pregnancy by increasing synthesis of various proteins. These proteins have defined interactions that allow the formation of matrix proteins to help fortify the uterine cervix. Toward the end of pregnancy, a series of hormone-mediated biochemical process takes place to degrade the collagen and fiber network to cause the cervix to ripen during labor. Failure to ripen the cervix during labor may delay its onset and cause complications. Current efforts to induce labor include pharmacologic, non-pharmacologic, mechanical and surgical methods.

Cervical ripening has primarily been performed in the inpatient setting. Due to a variety of reasons, such as cost and patient preference, the capacity to undergo outpatient cervical ripening is being explored. Cervical ripening options require ample time to be effective, making outpatient cervical effacement a more appealing option to some women. Significant evidence has been reported to draw conclusions on whether neonatal or postpartum harm have resulted from outpatient cervical ripening.

Prior to effacement, the cervix is like a long bottleneck, usually about four centimeters in length. Throughout pregnancy, the cervix is tightly closed and protected by a plug of mucus. Effacement is accompanied by cervical dilation. When the cervix effaces, the mucus plug is loosened and passes out of the vagina. The mucus may be tinged with blood and the passage of the mucus plug is called bloody show (or simply "show"). As effacement takes place, the cervix then shortens, or effaces, pulling up into the uterus and becoming part of the lower uterine wall.

Further Information: Signaling Pathways Regulating Human Cervical Ripening in Preterm and Term Delivery

Histologically, the cervix undergoes significant changes towards the end of gestation, allowing the ripening of cervix for the passage of birth delivery. First, there is an increase in the cervical synthesis of glycosaminoglycan hyaluronan (HA), which increases tissue hydration, thereby catalyzing the degradation of collagen and elastin-fibers. Second, there is an increase in the secretion of matrix metalloproteinases that also act to digest components of the extracellular matrix, including proteoglycans, laminin, and fibronectin, which are found in the cervical stroma (parametrium). Third, due to the nature of the cervical effacement process, enzymes and other mediators that regulate allergic and inflammatory responses are also involved. One of the immunomodulating factors, mast cells, is known to secrete inflammatory mediators that modulate the process of cervical ripening through mast cell degranulation. Histamine, one of the allergenic mediators released by mast cells, has shown to have causative relationship with cervical smooth muscle contractility. However, the research is not complete.

The Bishop score is the most common method of assessing the need for induction of labor. The scoring is based on a digital cervical exam and takes into consideration cervical dilation, position, effacement, consistency of the cervix and fetal station.

Cervical dilation, effacement and station are scored from 0 to 3. Cervical consistency and position are scored from 0 to 2. The total score ranges with a minimum of 0 and maximum of 13. A Bishop score of 6 and below indicates that induction is not favorable and no method of induction will be highly effective. In these cases, cervical ripening agents may be used. A score of 8 and above indicates induction of labor is favorable and the possibility of a vaginal delivery with induction will be similar to spontaneous labor.