The main medicines used to ripen the cervix are prostaglandins, synthetic versions of hormones your body naturally produces near the end of pregnancy. The two most common are dinoprostone and misoprostol. Oxytocin is sometimes used as well, though it plays a bigger role in stimulating contractions than in softening the cervix itself.
Why Cervical Ripening Is Needed
Before labor can progress, your cervix needs to soften, thin out, and begin to open. Your body does this naturally as your due date approaches, but sometimes labor needs to be induced before the cervix is ready. Providers assess cervical readiness using a scoring system called the Bishop score, which rates factors like how dilated, soft, and positioned the cervix is. A score of 5 or lower means the cervix is unfavorable for induction, and ripening medication is typically recommended before contractions are started.
How These Medicines Work
Your cervix is held firm by tightly packed collagen fibers, similar to the structural protein in tendons and ligaments. Prostaglandin medications trigger a chain of events that breaks down that collagen. Immune cells flood into the cervical tissue and release enzymes that dissolve the collagen fibers, causing them to fragment and leave the tissue. At the same time, the cervix absorbs more water and a substance called hyaluronic acid, which gives it a softer, more pliable texture. The combination of collagen loss and increased water content is what transforms the cervix from firm and closed to soft and stretchable, ready for labor.
Dinoprostone: The FDA-Approved Option
Dinoprostone is a synthetic form of prostaglandin E2 and is the only medication specifically FDA-approved for cervical ripening. It comes in two forms: a vaginal insert (sold as Cervidil) and a gel (sold as Prepidil).
The vaginal insert contains 10 milligrams of dinoprostone and releases the medication slowly, about 0.3 milligrams per hour, over up to 12 hours. It’s placed in the back of the vagina and has a thin retrieval string, similar to a tampon, so it can be removed when needed. You’ll be asked to lie down during placement and for about two hours afterward. The insert is removed after 12 hours, when active labor begins, or if any concerns arise with contractions or the baby’s heart rate. One practical advantage of the insert is that a provider can pull it out quickly if the medication causes problems.
The gel form is applied directly to the cervix and absorbs into the tissue. Unlike the insert, it can’t be removed once applied, which is an important distinction if side effects develop.
Misoprostol: The Off-Label Alternative
Misoprostol is a synthetic prostaglandin E1 analog originally developed to treat stomach ulcers. It’s widely used for cervical ripening, though this use is technically off-label, meaning the FDA hasn’t specifically approved it for this purpose. That doesn’t mean it’s unsafe or experimental. It has decades of clinical use and is included in major obstetric guidelines.
Misoprostol can be given vaginally, by mouth, or under the tongue. The most commonly recommended vaginal dose is 25 or 50 micrograms. It’s a small, inexpensive tablet, which is one reason it’s so widely used around the world. Once placed vaginally, the medication is absorbed with a very short active period in the bloodstream (under one hour), but its effects on the cervix and uterus last much longer. Because it can’t be physically retrieved like a dinoprostone insert, providers typically use lower doses and wait between applications to monitor your response.
Oxytocin’s Role
Oxytocin, given through an IV drip, is best known for strengthening contractions during active labor. It does contribute to cervical change, but primarily by driving contractions that put pressure on the cervix rather than by softening it chemically the way prostaglandins do. For this reason, oxytocin is often started after a prostaglandin has already done the initial ripening work. Providers typically wait at least 30 minutes after removing a dinoprostone insert before beginning oxytocin to avoid overstimulating the uterus.
Risks and Side Effects
The most significant risk with any of these medications is uterine tachysystole, a term for contractions that come too frequently. Normal labor involves contractions with rest periods in between, giving the baby time to recover. When the uterus contracts too often, it can reduce blood flow to the baby and cause changes in the baby’s heart rate. Research shows that about a quarter of tachysystole episodes are accompanied by heart rate changes, and the risk increases with higher doses of oxytocin in a dose-dependent pattern.
Other common side effects include nausea, diarrhea (especially with misoprostol, given its original use as a stomach medication), and cramping that starts before full labor contractions develop. Most of these are manageable and expected.
Who Should Not Use These Medications
Prostaglandins for cervical ripening are not appropriate for everyone. They are generally avoided if you have a uterine scar from a previous cesarean delivery (particularly a classical, or vertical, incision) or from a surgery that entered the uterine cavity. The concern is that strong contractions on a scarred uterus increase the risk of uterine rupture.
Other situations where cervical ripening medications are contraindicated overlap with situations where vaginal delivery itself isn’t safe: placenta covering the cervix, umbilical cord prolapse, a baby lying sideways, or an active genital herpes outbreak. Your provider will review your specific history before recommending a ripening method.
What the Experience Looks Like
If your provider recommends cervical ripening, the process usually starts in the hospital. With a dinoprostone insert, you can expect to have it placed, lie down for a couple of hours, and then move around while being monitored for up to 12 hours. With misoprostol tablets, you may receive one dose and then wait several hours before reassessment, with additional doses given if needed. Cramping and mild contractions often begin within a few hours. Some people progress into active labor from the ripening agent alone, while others need oxytocin afterward to establish a regular contraction pattern.
The total time from the start of ripening to delivery varies widely. For a first-time parent with a very unfavorable cervix, the process can take a full day or longer. This is normal and doesn’t mean something is wrong. Cervical ripening is the slow, preparatory phase that makes the more active phase of labor possible.