Which is better for induction of labor , if your cervix is determined to be “unfavorable” by your provider? Currently the method chosen is provider dependent based on BISHOP score and preference. (See our Instagram reel to understand what a BISHOP score is) If a cervix is thick and closed, it may be considered unfavorable for Induction of Labor. Initial induction options should include something that helps the cervix soften, so it can then dilate more easily; and something that helps the cervix open.
Let’s explore what research supports is the better option!
Induction of Labor Options for Low Bishop Scores
The two options for an unfavorable cervix are cervical ripening agents, such as Cytotec and cervidil, and Mechanical Dilators, such as membrane stripping, foley balloon, Cook Catheters, and Dilapan-S.
Cervical Ripening Agents: Make the Cervix Soft
Cervical Ripening agents are synthetic prostaglandins, which is a necessary hormone in the Ferguson Reflex for labor.
The goal of cervical ripening agents is to soften (efface) the cervix to initiate labor. They can cause contractions, but not always. The benefit?? You can have this method done even if you are 0cm dilated.
VBAC?? These are contraindicated in someone who has had a prior uterine surgery (c-section, myomectomy). So, cervical ripening agents will likely not be an option for Induction of Labor if you have had a prior uterine surgery.
One of the risks associated with cervical ripening agents is it can cause hyperstimulation of the uterus. Hyperstimulation means contractions are happening too close together and there’s not enough relaxation of the uterus in between contractions. Baby’s do not tolerate back-to-back contractions for very long. If there is very little relaxation between contractions, baby’s may have a harder time recovering and can cause the to go into distress.
With cervical ripening agents there are drugs to counteract it, but usually once the cervical ripening agents are given, especially Cytotec, we cannot take the drug back.
Mechanical Dilators: Open the Cervix
Mechanical dilators are a drug-free option that induces by stretching the cervix open using fingers, or some sort of medical object. Medical objects can include a foley bulb or cooks catheter. Both of these are inserted through the cervix, and apply pressure from the inside on the cervix to force it to dilate. This increase of pressure stimulates the release of hormones in the body to help initiate the Ferguson Reflex naturally to cause not only dilation but also effacement.
You need to be at least 0.5cm or a fingertip dilated to be a candidate for mechanical dilation. If you aren’t dilated at all, they will have to start with some sort of cervical ripening medicine. This is an important consideration for Induction of Labor if you are a VBAC.
Which to choose??
Which one is better? While it really is situation dependent because not everyone can be a candidate for both, one study did show that the cervical ripening agents, particularly vaginal Cytotec, is more effective than mechanical dilators at inducing labor. There was a higher rate of precipitous delivery/only Cytotec compared to the mechanical dilator group. More women delivered within 12 hours in the Cytotec group than the mechanical dilator group, and the mechanical dilator group had a higher incidence of prolonged labors compared to the Cytotec group.
After reading this study it made sense to me that the cervical ripening agents would work better than mechanical dilators because in my experience, they usually do a better job of softening out the cervix and sometimes kick starting labor than mechanical dilators. Even when someone is dilated >3cm but their effacement is less than 70/80% I have seen cervical ripening agents still used and that was all that was needed in Induction of Labor process.
Imagine your cervix was like a bunch of rubber bands. If we have 50 rubber bands, it is a lot harder to stretch those rubber bands open and keep them open. It’s possible, but much more challenging. Now imagine you only have 1 or 2 rubber bands; it is much easier to stretch those bands open and apply pressure to manipulate them to stay stretched and opened!
Learn more about induction of labor in our online & virtual childbirth education courses and in our Induction of Labor course!
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References
1. https://pubmed.ncbi.nlm.nih.gov/9158305/
2. https://anmrp.com/comparison-of-low-dose-vaginal-misoprostol-with-foley-catheter-balloon-as-preinduction-cervical-ripening-agents-in-term-pregnancies/