User:Brian.Chiu - UCSF PharmD./Cervical effacement

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 a normal, physiological process that occurs at the later end of pregnancy, it can also be induced through medications and procedures.

The cervix is located in the lower part of the uterus and connects the uterine cavity to the vagina. The cervix consists of two parts; the upper part lies in the pelvic/abdominal cavity and the lower part is intravaginal.

Background

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. 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. Cervical effacement is a component of the Bishop score and can be expressed as a percentage, from zero percent (not effaced at all) to 100 percent, which indicates a paper-thin cervix.

Traditionally, cervical effacement has been performed as an inpatient procedure that often requires substantial time and resources to accomplish. However, with the cost of care when cervical ripening is used in inpatient settings and for other reasons, some women may prefer to be at home during the cervical ripening process. With the incentives to reduce stress of the healthcare team and medicalization from the induction of birth, providers have also been exploring methods of cervical ripening in the outpatient settings.

Assessment of Cervical Effacement

The Bishop Score and Cervical Effacement

The Bishop score is the most common method of assessing the need of 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 between 0 and 13. A bishop score of 6 and below indicated that induction is not favorable. 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.

Cervical effacement is an important component of the Bishop score and is reported as a percentage. 0% indicates the cervix is at normal length, 50% indicates the cervix is half of the expected length and 100% effaced means the cervix is paper thin.

Other Methods of Assessing Cervical Effacement

Given that cervical effacement is measured as a percentage, this method requires a standard uneffaced cervix length. This requirement presents itself as an opportunity for error, miscommunication and inappropriate care in the process of assessing cervical effacement. Integrating the metric system of measurement of the cervix may reduce and eliminate this risk.

Many other methods of assessing and measuring the degree of cervical effacement are being studied. Elastography measures the stiffness and ability of the cervical tissue to deform under pressure. This is not able to be assessed manually and can be a useful parameter in predicting a preterm or full term delivery.

Contra-indications

Cervical ripening is contraindicated in pregnancies presenting with the following conditions:

• Less than 39 weeks of gestation, without medical indication
• Prior cesarean delivery
• Major uterine surgery

Contraindications to cervical ripening also include those of vaginal birth. Absolute contraindications can result in life-threatening events, and relative contraindications should be considered with caution. The absolute and relative contraindications to vaginal birth include, but are not limited to the following:

Absolute contraindications:

• Breech presentations (footling, frank, complete)
• Cord prolapse
• Fetus malposition
• Conjoined twins
• Mono-amniotic twins
• Placenta previa
• History of uterine rupture
• Active genital herpes infection

Relative contraindications:

• Fetal weight greater than 5kg in an individual with diabetes
• Fetal weight greater than 4.5kg in an individual without diabetes
• Non-reassuring fetal heart rate patterns

Risks/Complications

Labor induction poses different risks to the mother and the fetus. As such, risks and complications relating to cervical effacement can be classified as being a maternal or fetal risk.

Maternal Risks

Infection

Cervical ripening via transcervical balloon catheter can increase the risk of maternal infection. Approximately 11% of mothers develop an intrapartum infection, 3% a postpartum infection and 5% a neonatal infection. Only intrapartum infection was deemed a clinically significant risk.

Uterine Hyperstimulation

The risk of uterine hyperstimulation as it relates to labor induction is higher with dinoprostone and vaginally administered misoprostol than it is with oxytocin and mechanical methods.

Fetal Risks

Autism or Autism Spectrum Disorder (ASD)

Oxytocin dysregulation has been linked to Autism or autism spectrum disorder. As oxytocin is one of the methods used for cervical ripening, the Committee on Obstetric Practice at the American College of Obstetricians and Gynecologists conducted a review of existing research regarding this link, and concluded that there was insufficient evidence of a causal link between cervical effacement via oxytocin and autism/ASD.

Fetal Distress or Hyperstimulation

Low dose oral misoprostol for the purpose of labor induction, is associated with a lower risk of fetal distress than vaginally administered misoprostol.

Vaginally administered Dinoprostone is associated with an increased risk of fetal hyperstimulation with or without fetal heart rate abnormalities.

Cervical Ripening in the Outpatient Setting and the Inpatient Setting

Results from a systematic review of the literature found no differences in cesarean delivery nor neonatal outcomes in women with low-risk pregnancies between inpatient or outpatient cervical ripening.

Methods

moved this from lead can delete if not needed: Cervical ripening is also part of the process of induction of labor, where medical interventions such as use of prostaglandin and oxytocin medications, balloon catheters, and membrane sweeping are utilized to help start labor.

Pharmacologic

• Oxytocin

Oxytocin is one of the most commonly used medications for cervical effacement. It is given as an infusion to either start or increase uterine contractions. Epidurals are often used together for pain. Oxytocin may also be used in the setting of amniotomy as well as balloon catheters to further contractions.

• Misoprostol

Misoprostol is a medication that can cause contractions for cervical effacement. When used with balloon catheters, vaginal delivery was more likely to occur within the next 24 hours after initiation. It is known as a type of prostaglandin.

• Dinoprostone

Also in the class of prostaglandins, dinoprostone increases contractions. It is available in both gel and vaginal insert form and while both are safe and efficacious, one study has found that in those with a bishop score of less than or equal to 4, the vaginal insert seemed to be more effective in spontaneous vaginal delivery by about 20%.

Non-Pharmacologic

• Red raspberry leaves

Red raspberry leaf tea is an herbal option for cervical effacement. In a retrospective observational study conducted in 1999, while there wasn't significant difference in time for second and third stage of labour, the "mean time in first stage of labour is also substantially lower in the raspberry leaf group". The data, however, was not proven to be statistically significant.

• Hot bath

Mechanical

• Balloon Catheter

Balloon Catheters are catheters that can be inserted into the cervix in the setting of pregnancy to induce labor. Saline is used to inflate the balloon, causing increased pressure to the cervix, which in turn, induces labor.

• Hygroscopic Dilator

Hygroscopic dilator is a dilator that is inserted into the cervix and expands in size as it absorbs genital tract moisture. They can also be used for early termination of pregnancy.

According to a study conducted in Japan from 2012-2014, the rate of delivery of women at term seemed to be equivalent between the group that used ballon catheter and that of the hygroscopic dilator.

Surgical

• Amniotomy

Amniotomy is a procedure where a hook is inserted into the amniotic membranes to puncture, causing the amniotic fluid to drain from the amniotic sac that holds the fetus.