Cervical ripening: overview, uterine features, cervical ripening (2023)

Bishop scores are somewhat subjective, but a score of less than 5 suggests further maturation is needed, while a score of 9 or higher suggests maturation is complete. No maximum has been set for the number of doses of a cervical ripening agent that can be administered. If the patient has no urgent indication for delivery and fetal well-being parameters are reassuring, the patient may even be discharged to return in a few days for another induction attempt. Good clinical judgment is essential. A variety of methods have been developed to induce cervical ripening in preparation of the cervix for labor and delivery.[3]


Two forms of PGE2 (Dinoprostona) are commercially available. In randomized studies, the two forms are equivalent in their effectiveness. The first is Prepidil, which is formulated as a gel and placed in the cervix, but not through the internal os. The application (3 g gel/0.5 mg dinoprostone) can be repeated in 6 hours without exceeding 3 doses in 24 hours. The second is Cervidil, which contains 10mg of dinoprostone embedded in a mesh and placed in the posterior vaginal fornix. This allows for a controlled release of dinoprostone over 12 hours, after which it is removed.

Comparison between the use of the intravenous lineOxytocinalone with a combination of oxytocin and vaginally or intracervically administered PGE2 show that prostaglandins lead to a significantly lower caesarean section rate and a higher proportion of vaginal deliveries within 24 hours. However, patients with ruptured membranes at the time of labor induction had a higher rate of chorioamnionitis than those receiving vaginal or intracervical PGE2.[4]

Prostaglandin E1 analogue (Misoprostol) usage has been described in a number of articles. This is a synthetic prostaglandin marketed as an anti-ulcer agent under the trade name Cytotec. A quarter of a tablet (25 mcg), which can be crushed and placed on the cervix, has been shown in many studies to be very effective in inducing cervical ripening and labour. The application of the drug can be repeated every 4 hours.

Two meta-analyses comparing randomized trials of vaginal misoprostol to dinoprostone found a higher rate of vaginal deliveries within 24 hours and similar rates of cesarean sections in the misoprostol groups, and therefore concluded that misoprostol is the more effective agent.[5, 6]

Misoprostol has also been administered orally (50–100 mcg, which can be repeated every 4 hours), but the vaginal route appears to be more effective. Vaginally administered misoprostol has been used for cervical ripening and labor induction in pregnancies complicated by oligohydramnios. These patients were not at increased risk of adverse perinatal outcomes compared to patients with normal amniotic fluid volume. Please note that the US Food and Drug Administration classifies Cytotec as a Pregnancy Category X drug. The manufacturer has been ambivalent about this off-label use of the drug, and the Food and Drug Administration only recognizes that misoprostol is used during pregnancy.

The American College of Obstetrics and Gynecology (ACOG) Committee on Obstetric Practice recommends that misoprostol not be used for postpartum inductionCaesarean sectionor major uterine surgery due to significant riskruptured uterus.[7]

The main risk of the above prostaglandin preparations is uterine hyperstimulation. The woman and fetus should be monitored for contractions, fetal well-being, and changes in Bishop's Cervical Score. Finally, Christensen et al. demonstrate that the combination of induction with oxytocin followed by dinoprostone use is safe and significantly shortens the time from induction to delivery.[8]

The exception to this appears to be women with previous caesarean births. The ACOG Committee on Obstetric Practice, in its review of the relevant literature, notes that sequential use of prostaglandins and oxytocin appears to increase the risk of uterine rupture in women who have had a previous cesarean section.[7]

A randomized controlled trial by Al-Ibraheemi et al., in which 200 patients were randomly assigned to a group with cervical ripening with concomitant use of misoprostol and a transcervical Foley balloon and a group with misoprostol alone, reported that the combined group had a longer time to delivery (15.0 hours vs. 19.0 hours in the misoprostol monogroup [p=0.001]).[9]


A 30 to 50 mL Foley catheter filled with saline is effective in inducing cervical ripening and dilatation. The catheter is inserted into the uterus and the balloon is inflated. Direct pressure is then applied to the lower segment of the uterus and cervix. This direct pressure causes stress on the lower uterine segment and probably the local production of prostaglandins.

In some studies, the catheter is combined with a saline solution as an extraamniotic infusion.[10]There is no evidence that extraamniotic saline infusion (EASI) increases the risk of chorioamnionitis.[11]A meta-analysis involving 27 studies and 3532 patients found that there was no difference between the Foley balloon and the use of PGE2 in the rate of caesarean section. This study was hampered by significant study heterogeneity and a subgroup analysis suggested that the Foley balloon combined with oxytocin and EASI may have a higher vaginal delivery rate and a lower tachysystole rate.[12]

The PROBAAT study compared the efficacy and safety of labor induction with a Foley catheter versus prostaglandin E2 vaginal gel induction. They found that outcomes were similar in women with an unfavorable cervix at the time of delivery, with fewer maternal and neonatal side effects associated with Foley catheter use.[13]

Low dose oxytocin infusion

In this method, a low-dose oxytocin infusion is given with a dose escalation of 1 to 4 mU/min. Ferguson et al. demonstrated that this procedure is comparable to intravaginal misoprostol for cervical preparation.[14]Because of the ease of shutting off the oxytocin infusion, they suggested that this method might play a preferential role in high-risk patients whose fetuses are at increased risk of labor intolerance.


mifepristona(formerly known as RU 486) is a potent antiprogesterone and antiglucocorticoid that acts by binding to progesterone and glucocorticoid receptors. Although individual randomized trials have shown favorable results for its use in labor induction, a review of the Cochrane database concluded that data were insufficient to support its use in labor induction. This review found a decrease in cesarean delivery rates with the use of mifepristone, suggesting potential future areas of research.[15]

Hygroscopic dilators

There are several products available that can be placed on the cervix and dilated by absorbing water. Laminaria are made from dried seaweed. The commercial products Dilapan and Lamicel are made from synthetic hygroscopic material. Several dilators are inserted into the cervix, as many as will fit, and expand over 12 to 24 hours as they absorb water. The absorption of water causes the dilators to expand and the cervix to open. They probably work the same way as the balloon catheter. Women do not require prophylactic balloon catheter antibiotics or hygroscopic dilators unless there are specific indications, such as: B. The need for prophylaxis against subacute bacterial endocarditis (SBE).

peel membrane

Manual separation of the amniotic membranes from the cervix is ​​believed to induce cervical ripening and the onset of labor. The mechanism is unknown, but it has been postulated that mechanical disruption of this tissue causes an increase in local prostaglandins through induction of phospholipase A2 in the cervical and membrane tissues. Such a postulate is certainly consistent with the known stimulation of cervical ripening by prostaglandins. However, there is currently no clear evidence that removing the membrane significantly reduces the length of pregnancy. The authors of a review of the Cochrane database on the subject concluded that this practice offers no clinically meaningful benefits.[sixteen]

Nitric Oxide Donors

Studies on the use of nitric oxide donors for cervical ripening are ongoing with conflicting results. Small preliminary studies for evaluationmononitrato de isosorbida(40 mg) and glyceryl trinitrate showed encouraging results. However, randomized controlled trials comparing misoprostol with and without isosorbide mononitrate have shown conflicting results. In addition, a review of the Cochrane database of 8 studies involving 718 patients evaluating the use of nitric oxide donors for cervical ripening in first-trimester surgical abortions found them to be inferior to prostaglandins and associated with more side effects.[17, 18, 19]

A randomized, double-blind, placebo-controlled study by Schmitz et al. also cast doubt on the use of nitric oxide donors in cervical ripening and found that they are no more effective than placebo in reducing the rate of caesarean section in nulliparous women with ongoing cancer. the pregnancy. The study of nullipara women at 41 weeks gestation included 678 patients receiving vaginal isosorbide mononitrate and 684 women receiving placebo, all on an outpatient basis. The researchers found that the caesarean section rate was almost identical in the isosorbide mononitrate and placebo groups (27.3% vs. 27.2%) and that side effects were more common in women treated with the nitric oxide donor than in the other patients (78.8% vs. 27.2%). % versus 27.9%).[20]


Based on the results of a number of animal studies, relaxin was predicted to have an effect on cervical ripening in humans. The findings that porcine relaxin induces cervical ripening in humans support this conclusion. Paradoxically, human relaxin has no effect on the human cervix, and relaxin is not currently used in cervical ripening or labor induction. The reason for the difference between the species is unknown, and the role of human relaxin in human birth is questioned.

In addition, animal studies suggest this supplementHyaluronidasecan shorten labor and improve induction success.[21]Future research in these and other areas may lead to better methods of cervical ripening and labor induction.

Summary of induction of cervical ripening

Induction of cervical ripening is essential for the successful induction of labor in a pregnant patient whose cervix has not undergone the ripening process. Cervical ripening allows uterine contractions to effectively dilate the cervix. The uterine pressure required to dilate a mature cervix is ​​believed to be about 1,600 mm Hg, while the pressure to dilate an immature cervix is ​​estimated to be more than 5 times or 10,000 mm Hg.

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