Pregnancy termination: Cervical preparation for procedural abortion

INTRODUCTION — Procedural abortion may be performed by uterine aspiration in the first trimester and by dilation and evacuation (D&E) in the second trimester. Although complications are rare, the risk can be decreased by preparing the cervix with dilators and/or administration of cervical ripening agents, which decrease cervical trauma during the procedure and facilitate evacuation of the uterus [1-3].

Cervical preparation prior to procedural abortion is reviewed here; the uterine aspiration and D&E procedures are discussed separately.

●(See "First-trimester pregnancy termination: Uterine aspiration".)

●(See "Overview of second-trimester pregnancy termination".)

●(See "Second-trimester pregnancy termination: Dilation and evacuation".)

APPROACH BY GESTATIONAL AGE — The key determinant to our approach to cervical preparation is gestational age. Other factors that guide the approach include a history of cesarean birth or cervical surgery, uterine anomalies, or fetal anomalies that result in an increased biparietal diameter. (See 'Special circumstances' below.)

<12 weeks — At <12 weeks of gestation, we recommend not using cervical preparation with osmotic dilators or medications. Typically, mechanical dilation alone is safe and effective (see 'Role of mechanical dilation' below). This recommendation is consistent with the Society of Family Planning guidelines, which advise against routine cervical priming with misoprostol or osmotic dilators in the first trimester [4]. They note that routine cervical preparation in the first trimester can delay the procedure and is associated with side effects.

The best available data regarding the lack of value of cervical preparation in first-trimester abortion are from a multicenter randomized trial of nearly 5000 patients at <13 weeks that compared use of misoprostol (400 mcg per vagina) with placebo three hours prior to D&E [5]. Although misoprostol reduced the rate of incomplete abortion (<1 versus 2 percent), the absolute effect was modest, and the number needed to treat to prevent re-evacuation was 1 in 72. Importantly, the risk of cervical injury without cervical preparation was very low (<1 percent) and was not further reduced with misoprostol; use of misoprostol, however, significantly increased the frequency of abdominal pain (55 versus 22 percent), vaginal bleeding (37 versus 7 percent), and nausea (7 versus 4 percent).

12 to <14 weeks — At 12 to <14 weeks of gestation, we suggest cervical preparation with osmotic dilators or medications for patients in whom mechanical dilation may be more difficult and, thus, are at an increased risk of cervical injury. These patients include:

●Nulliparous patients.

●Adolescents (age ≤17 years) [4], even when analyses controlled for parity [6,7].

●Patients with mechanical barriers to dilation, such as a history of cervical surgery (eg, loop electrosurgical excision procedure or cold knife cone), cervical stenosis, or a cervical fibroid that may impede dilation.

Some clinics also begin using cervical preparation at 12 weeks in patients at low risk of cervical injury, such as multiparous patients with normal cervixes (table 1). However, cervical preparation can be omitted in clinical situations in which it is not feasible and an experienced provider determines that proceeding without preparation is appropriate.

When cervical preparation is given between 12 to <14 weeks, we advise using one of the regimens presented in the table (table 1). Available data do not strongly support a recommendation for one cervical preparation modality over another [4]. Misoprostol is the cervical preparation method typically used [4], and the route and time interval between misoprostol administration and the procedural abortion vary by institution [8,9]. Additional information on the use of these modalities is available below. (See 'Cervical preparation modalities' below.)

14 to <18 weeks — At 14 to <18 weeks of gestation, we suggest using cervical preparation in essentially all patients. An exception would be a clinical situation in which cervical preparation is not feasible and an experienced provider determines that proceeding without preparation is appropriate. The recommendation is based on expert opinion and observational data from nearly 12,000 patients that show a marked decrease in cervical laceration with use of cervical preparation in the second trimester [1].

The two most common protocols (same-day and two-day) for cervical preparation between 14 to <18 weeks of gestation are detailed below. The evidence supports the efficacy and safety of both protocols [8,10,11]; thus, patients should be counseled about and offered both options, with some exceptions regarding clinic resources or individual clinical situations, as described below (see 'Two-day protocol' below). Patients can be informed that:

●While the two-day protocol using overnight laminaria results in significantly more dilation than same-day Dilapan-S, both protocols result in similar blood loss, procedural difficulty, and complication rates [10,12]. In a retrospective noninferiority study including over 1300 patients undergoing pregnancy termination between 14 and 16 weeks gestation, acute complications (eg, hemorrhage, hospital transfer or admission, unplanned procedure) for same-day cervical preparation were noninferior to overnight cervical preparation and low in both groups [11].

●Potential advantages of the same-day procedure are that it offers less time off work, less need for extra childcare, and less time away from home, especially if the patient must travel far to get to the clinic (eg, there are no clinicians who can perform a D&E in their area, their state has legal restrictions on gestational age limits). However, same-day protocols entail arriving at the clinic several hours before the procedure for cervical preparation.

●Potential advantages of the two-day protocol are that the patient avoids a prolonged waiting time at the clinic and the total time in clinic may be shorter, even though two clinic visits on consecutive days are required. A potential disadvantage is that overnight dilation is associated with unique risks, such as bleeding, rupture of membranes, infection, preterm labor, and extramural delivery, although these are rare. (See 'Complications' below.)

Same-day protocol — The same-day protocol involves administering misoprostol alone, Dilapan-S alone, or both three to four hours prior to the procedural abortion (table 1). While clinical practice varies, use of either misoprostol or Dilapan-S appears to be safe and effective. In a randomized trial comparing same-day Dilapan-S versus buccal misoprostol, there were no differences in procedure duration, complications, or patient preference, although mechanical dilation was easier after Dilapan-S [13].

Two-day protocol — The two-day protocol involves placing osmotic dilators on day 1 and performing the procedural abortion on day 2 (table 1). In one of our practices, misoprostol is given just prior to the procedural abortion as a uterotonic agent rather than for cervical preparation.

The two-day procedure is preferable to the same-day protocol in select circumstances, primarily when a greater degree of dilation is needed or dilation is expected to be difficult, as in the following situations:

●Fetal anomalies that lead to a larger biparietal diameter.

●An intact procedure is preferred (eg, if an autopsy is desired).

●Uterine anomalies that may necessitate more dilation, such as lower uterine segment fibroids.

●History of cervical surgery (eg, cryotherapy or conization).

●Nulliparous patients.

Mifepristone has been studied as an alternative to placing osmotic dilators on day 1 of the two-day protocol and appears to be effective. In a randomized trial (n = 50) in which patients at 14 to 16 weeks were assigned to mifepristone on day 1 versus overnight dilators, there were no differences in procedure duration, and patients preferred mifepristone [14]. However, most providers in the United States do not use mifepristone at this gestational age. This is likely because mifepristone is relatively expensive and because a significant proportion of procedures at this gestational age are performed in one day using misoprostol.

≥18 weeks — At ≥18 weeks of gestation, we recommend cervical preparation for essentially all patients. An exception is in clinical situations in which cervical preparation is not feasible and an experienced provider determines that proceeding without preparation is appropriate. The basis for this recommendation is observational data from nearly 12,000 patients who did or did not receive laminaria for cervical preparation; a marked decrease in cervical laceration was seen with the use of cervical preparation (5 to 8 percent without laminaria versus approximately 1.5 percent with laminaria) [1].

Clinical protocols and provider judgment are generally based on achieving the best balance of dilators, mifepristone, and misoprostol to achieve adequate dilation, prevent complications, and minimize side effects (eg, pain, nausea). In this gestational age group, most clinicians use a two-day protocol with the placement of osmotic dilators, with or without mifepristone, on day 1 and perform the D&E procedure, with or without misoprostol, on day 2 (table 1).

At 18 weeks, there are insufficient data to make a strong recommendation for use of overnight osmotic dilators alone or overnight dilators with either mifepristone or misoprostol. However, for patients at 20 to <24 weeks of gestation, data suggest that, compared with using dilators alone, the use of overnight osmotic dilators with mifepristone results in less difficult dilation, shorter procedure time, and more consistent ability to begin the D&E after one rather than two nights of dilators [15,16]. A randomized trial included patients at 19+0 to 23+6 weeks (n = 148) and compared three groups: overnight dilators alone, overnight dilators with mifepristone, and overnight dilators with misoprostol on the day of D&E [16]. Procedure duration was slightly longer in the group with dilators alone (13 versus 9 versus 10 minutes). Fewer procedures were reported to be difficult by the operator in the mifepristone group (dilators alone: 19 percent; dilators with mifepristone: 4 percent; dilators with misoprostol: 19 percent). There were more complications in the group with dilators alone (seven versus two versus one complication). Patients given misoprostol had significantly more pain, fever, and chills. Patient satisfaction was similar across all groups.

As stated above, the two-day protocol is preferred at gestational ages ≥18 weeks. In limited situations, the following may be appropriate, although not common practice:

●If dilation is insufficient after the overnight dilators are removed, further dilation can be achieved by using misoprostol, additional Dilapan-S, or a second set of overnight dilators, and a D&E can be performed on day 3. (See 'Complications' below.)

●Same-day cervical preparation may be possible up to 21 weeks (eg, if a patient travels far and cannot stay overnight); this should be performed only by experienced clinicians [17].

Dilapan-S is the osmotic dilator that is usually preferred, but laminaria may be used.

Practice varies regarding whether misoprostol is used on the day of the procedure. Despite increasing cervical dilation, misoprostol causes more gastrointestinal side effects than mifepristone and more cramping and bleeding [18], and, therefore, some providers do not use misoprostol. It should be noted that mifepristone hastens the dilatory effects of misoprostol and increases the risk of pregnancy expulsion. In a trial of mifepristone with misoprostol or misoprostol alone [19], among the 450 participants who received combined mifepristone and misoprostol, there were 15 patients who had an expulsion of pregnancy prior to D&E, and two of the expulsions occurred prior to misoprostol administration. Therefore, the use of mifepristone must be taken into account prior to determining the length of time any particular patient receives misoprostol. If a patient who has received mifepristone experiences excessive cramping or bleeding while they are waiting the three to four hours after the misoprostol dose, we will expedite the patient to the operating room to perform the abortion and to prevent pregnancy expulsion.

Representative studies for the management of cervical preparation at ≥18 weeks of gestation include the following:

●In a randomized trial with patients from 19+0 to 23+6 weeks of gestation, the interventions were overnight dilators with mifepristone and then misoprostol on the day of the D&E, and two days of osmotic dilators and misoprostol on the day of the D&E. There were no differences in initial dilation or procedure duration. However, patients preferred overnight dilation with mifepristone more than two nights of dilation without mifepristone [20].

●A follow-up trial including 75 patients in the same gestational age cohort compared three groups that varied by treatment on the day before the procedure; all groups received misoprostol on the day of the D&E [21]. The groups included treatment with mifepristone alone, dilators with mifepristone, and dilators with placebo. Patients treated with mifepristone alone had less dilation and longer procedure duration than the other groups, but duration was similar for dilators with mifepristone compared with dilators without mifepristone (mifepristone alone: 18.5 minutes; dilators with mifepristone: 12 minutes; dilators with placebo: 13 minutes). There were more complications in the mifepristone alone group (mainly cervical laceration or uterine perforation), but this did not reach statistical significance (seven versus zero versus one complication). Patients in the two groups treated with dilators and mifepristone rated their overall experience higher than mifepristone alone.

Special circumstances

●Prior cesarean birth – Patients with one or more prior cesarean births require similar cervical preparation to other patients. In the second-trimester labor induction literature, misoprostol alone is often given at 20 to 24 weeks of gestation without an increased risk of cesarean scar dehiscence or rupture in patients with one prior cesarean [22]. It is important, however, to look for signs of abnormal placentation at the time of ultrasound in any patient with a prior cesarean. (See "Overview of second-trimester pregnancy termination", section on 'Placental abnormalities' and "Overview of second-trimester pregnancy termination", section on 'Prior uterine scar'.)

●Placental abnormality – The presence of a placental abnormality (ie, low-lying placenta, placenta previa, placenta accreta spectrum) does not preclude the use of cervical preparation. This is discussed in more detail separately. (See "Overview of second-trimester pregnancy termination", section on 'Placental abnormalities'.)

●Uterine anomaly – Among patients with a uterine anomaly, it is important to have an ultrasound preoperatively and, if possible, intraoperatively. When there is more than one cervix, the correct canal must be identified and dilated. If the fetus cannot be reached, the patient may need to be referred for an induction. (See "Overview of second-trimester pregnancy termination", section on 'Uterine anomaly'.)

●Prior cervical procedure – Patients with a prior cervical procedure, such as loop electrosurgical excision procedure or cryotherapy, may have a very small or short uterine cervix. As long as the os can be identified and dilated, the cervix can be prepared. In some cases, the cervix cannot be seen. Bimanual examination and ultrasound may be necessary to locate the canal. If the cervix itself cannot be located on examination and by ultrasound, misoprostol alone can be used to try to dilate the cervix, or the patient will need to be referred for an induction. (See "Cervical intraepithelial neoplasia: Diagnostic excisional procedures", section on 'Late complications'.)

●Multiple gestation – Even with more than one fetus, the general approach will be similar to that in patients with singleton pregnancies. (See "Overview of second-trimester pregnancy termination", section on 'Multifetal gestation'.)

●Fetal anomalies – Fetal anomalies that result in an increased biparietal diameter may necessitate additional cervical preparation to achieve greater cervical dilation.

●Rupture of membranes – Osmotic dilators may be used in patients with rupture of membranes with or without chorioamnionitis. There is no evidence that use of dilators exacerbates infection in such patients. This is discussed in detail separately. (See "Overview of second-trimester pregnancy termination", section on 'Chorioamnionitis'.)

CERVICAL PREPARATION MODALITIES — There are several modalities for cervical preparation prior to procedural abortion; they may be used alone or in combination. Several factors guide the choice of cervical preparation method, including safety, the degree of cervical dilation required to perform the procedure, surgical skill, and patient comfort. (See 'Approach by gestational age' above.)

Osmotic dilators — Osmotic dilators are small, sterilized rods that are placed in the cervical os and dilate gradually as they absorb moisture. They are placed from four hours up to two days prior to the procedure, depending on the type of osmotic dilator used, the degree of dilation required, and whether a concomitant cervical ripening medication is used. Typically, they are used for cervical preparation beginning at 12 to 14 weeks of gestation, but this varies by clinician.

Types — The two main types of osmotic dilators that are commercially available are laminaria japonica and Dilapan-S (table 2).

●Laminaria japonica – Laminaria japonica dilators (picture 1) are sterilized dried seaweed stems that function by absorbing fluid and expanding slowly. Dry laminaria range in size from a diameter of 2 to 10 mm and are approximately 60 mm in length. Typically, laminaria are placed on the day prior to the procedure and left in place for approximately 24 hours. By that time, each laminaria has expanded to more than 2.5 times its dry diameter [23,24]. In vitro, a 3 mm laminaria will expand to an average of 9.8 mm.

A disadvantage of laminaria is that, because they are a natural product, some laminaria rods may expand more than others. These irregularities in expansion of laminaria can result in variability of dilation among patients despite the same number of laminaria used and, thus, increased need for mechanical dilation. (See 'Role of mechanical dilation' below.)

●Dilapan-S – Dilapan-S (picture 2) is made of hydrophilic polymers. It is available in 3 and 4 mm diameters and is 55 mm in length. Initial dilation occurs over 3 to 6 hours and continues to expand over the course of 24 hours to over 3.5 times its dry diameter. In vitro, the 3 mm Dilapan-S expands to an average of 10.3 mm [24]. In an in vivo cohort study including 44 patients undergoing induction of labor at term, the 4 mm Dilapan-S expanded to 7.9 mm (mean) in 6 hours and 10.8 mm (mean) in 12 hours; concurrent placement of a dry or saline-saturated gauze at the external os resulted in similar results [25].

An advantage of Dilapan-S is that it dilates more quickly and to a more consistent diameter than laminaria. In addition, fewer Dilapan-S than laminaria are needed to generate the same cervical dilation. A disadvantage is that Dilapan-S may dilate unevenly across the length of the dilator. This is referred to as "dumbbelling," during which the proximal and distal ends dilate, but the portion that is within the internal cervical os does not. This forms a dumbbell or hourglass shape that can result in inadequate dilation and need for subsequent mechanical dilation. At times, dumbbelling can make removal of Dilapan-S very difficult, which may necessitate further cervical preparation and delay of the procedure. (See 'Complications' below.)

Comparative efficacy — Both laminaria and Dilapan-S appear to have similar efficacy of cervical preparation. In a randomized trial (n = 180) comparing Dilapan-S with laminaria that evaluated two gestational age cohorts, 18 to <21 weeks and 21 to <24 weeks, there were no differences in operative duration between dilator types in either gestational age cohort and no differences in procedure difficulty, pain, or dilation [26]. Of note, there were 24 cases that could not be completed on the first attempt and required adjunctive methods; 75 percent of those cases were in the laminaria group, and there was a significantly higher rate of need for adjunctive methods with laminaria in the earlier gestational age cohort.

Number required — There are no studies to guide the number of osmotic dilators that should be placed in the cervical os, and expert opinion varies widely on the optimal number. Institutions or clinics tend to have shared practices or protocols to guide the number, timing, and type of dilator. Given the wide range in practices and the lack of high-quality data to evaluate each protocol, the number of dilators used for cervical preparation will continue to be individualized until best practices can be established. Some options include:

●Placing dilators until they fit snugly, but not tightly, in the cervix.

●The total number of osmotic dilators equaling the patient's "gestational age minus 10."

●Placing five Dilapan-S for 20 weeks of gestation with an additional Dilapan-S for each subsequent week of gestation [27,28].

●Placing three Dilapan-S for 18+0 to 21+6 weeks of gestation with adjuvant misoprostol for three to four hours [29].

There is no standard regarding a maximum number of dilators that may be placed; however, the authors have rarely seen a need for more than 12 Dilapan-S or 14 laminaria, especially when combined with mifepristone.

Procedure — For analgesia, we administer 600 to 800 mg ibuprofen approximately 30 minutes before and a paracervical block immediately before osmotic dilator placement.

To decrease the risk of infection, antibiotics are routinely administered before a procedural abortion. In our practice, we give one dose of azithromycin 500 mg orally at the time of dilator placement (table 3) [30]. The advantages of azithromycin include its long half-life (a second dose is not needed at the time of the procedural abortion if performed within 24 hours of the initial dose of antibiotics) and low side effect profile (patients experience less nausea compared with other antibiotics, such as doxycycline). Other providers defer antibiotics at the time of dilator placement and rather administer antibiotics only preoperatively. This is discussed in more detail elsewhere. (See "First-trimester pregnancy termination: Uterine aspiration", section on 'Antibiotic prophylaxis' and "Second-trimester pregnancy termination: Dilation and evacuation", section on 'Prophylactic antibiotics'.)

The cervix is typically sterilely prepared (though cleansing the cervix has not been shown to prevent abortion-related infection [31]), and stabilized with a tenaculum. Each dilator is grasped with forceps and placed carefully into the cervical canal until it traverses both the external and internal os. After dilator placement, we place a single sterile gauze with a bacteriocidal cleansing fluid (eg, iodine or chlorhexidine) in the vagina. Practices vary, and some clinicians do not place gauze at the time of dilator placement.

Patients undergoing cervical preparation with osmotic dilators should have access to a clinician 24 hours a day. We tell patients to call with any concerns, especially the following:

●Bleeding (soaking more than one pad per hour)

●Fever ≥101°F

●Rupture of membranes

●Pain that does not resolve with ibuprofen 800 mg

●Expulsion of one or more dilators

●Any concerns that labor is starting

The patient is also informed that if the gauze is expelled, it should be thrown away. However, if any dilators are expelled, they should be placed in plastic wrap or a bag, and the patient should bring them on the day of surgery. This is important so that dilators can be counted to ensure all have been removed.

Complications — Potential complications are rare and include the following:

●Onset of labor – Ruptured membranes can occur, but onset of labor is rare, and extramural delivery is even more infrequent unless a feticidal agent was administered [2,32-34]. (See "Induced fetal demise".)

●Infection – There are few reports of infection after dilator placement [35,36]. The low infection rate could be the result of dilator sterilization or the routine practice of prophylactic antibiotics for procedural abortion (table 4).

●Uterine perforation – If the dilator is not placed appropriately inside the cervical canal, a "false passage" may be created that can increase the risk of a subsequent perforation. Therefore, it is imperative to keep the dilators within the cervical canal, and if there is any concern regarding the cervical canal anatomy, an ultrasound should be used to verify the location of the osmotic dilator.

●Anaphylaxis – Anaphylaxis to laminaria has been documented in case reports [37,38]. The authors are not aware of any cases of hypersensitivity to the synthetic dilator Dilapan-S.

Other potential issues include:

●Difficult removal – At the time of surgery, if the dilators cannot be removed easily, excessive force should not be used. If a combination of laminaria and Dilapan-S was placed, removal of the laminaria first may facilitate removal of the remaining dilators. Other options to facilitate removal include:

•Placing misoprostol 400 to 600 mcg vaginally for two to three hours.

•A subsequent dose of misoprostol 400 mcg may be given either vaginally or buccally for one to two hours [39].

•Changing the route of misoprostol administration (eg, from vaginal to buccal) and waiting an additional two to four hours.

●Inadequate dilation – After the dilators are removed, the amount of dilation may be inadequate. Some providers will attempt to pass a Sopher or Bierer forceps to ascertain if dilation is adequate. As with cases of dumbbelled dilators, sometimes, the internal os is not dilated as widely as the external os. An attempt to dilate the internal os can be made using mechanical dilators. It is crucial to avoid excessive force during mechanical dilation to prevent cervical laceration.

If the cervix is inadequately dilated and adequate mechanical dilation cannot be obtained, options include the following:

•Administer misoprostol 400 mcg by buccal or vaginal route and wait three to four hours.

•Insert additional Dilapan-S (with or without vaginal misoprostol) and wait at least four hours.

•Insert additional dilators and have the patient return the next day.

●Expulsion – Expulsion of dilators without sufficient dilation is rare, especially when dilators are placed correctly. It is important that patients are counseled not to discard dilators if they are expelled. We recommend they place the dilator in a bag or plastic wrap if one is expelled. Counting the dilators is the best way to ensure no dilator is left in the uterus after the procedure.

Cervical ripening medications — Cervical ripening agents are medications that help soften the cervix and may be used alone or in combination with osmotic dilators [8,40].

Misoprostol — Misoprostol is a prostaglandin E1 analog that is commonly used for cervical preparation. It is inexpensive, stable at room temperature, and, in addition to cervical ripening, can also increase uterine tone to treat excessive bleeding due to uterine atony [41].

Misoprostol is usually administered buccally or vaginally for cervical preparation but can be given via other routes (oral, sublingual, and rectal); many different dosing regimens are available, and all increase baseline cervical dilation [4,42,43]. Side effects of misoprostol may include gastrointestinal upset, vomiting, cramping, or vaginal bleeding.

Vaginal and sublingual routes of misoprostol appear to achieve more dilation and have fewer side effects than oral misoprostol [44-48]. A systematic review comparing sublingual with vaginal administration found improved dilation with sublingual administration but more nausea [49]. Buccal administration has similar efficacy as vaginal administration but with fewer side effects [42,50].

Expulsion of pregnancy prior to the procedure may occur after misoprostol treatment. Expulsion is more common with a longer interval from misoprostol administration to the abortion procedure [40]. In one study of 450 patients who received misoprostol, 3 had expulsions prior to their D&E procedure [19].

Role of a balloon catheter — A balloon catheter (eg, Foley bladder catheter) may be used alongside misoprostol to facilitate procedural abortion.

Use of same-day and overnight balloon catheters have been described. In a retrospective study including 290 patients between 18 0/7 to 21 6/7 weeks of gestation undergoing cervical preparation and procedural abortion in a single day, an 18-french 30 cc Foley catheter was placed transcervically and inflated with 35 mL sterile water; misoprostol 800 mcg was administered buccally at the same time of Foley placement and then every four hours according to physician discretion. The average time between misoprostol and D&E was 7.2 hours and the average length of the D&E procedure was 12 minutes. While the protocol requires patients to remain in clinic throughout their cervical preparation, the D&E can be completed in a single day and may decrease barriers to care when compared with protocols requiring overnight dilation. Similarly, in a retrospective case series including 43 patients between 17 0/7 and 24 2/7 weeks gestation undergoing overnight cervical preparation with a Foley catheter plus misoprostol, adequate dilation was achieved in the majority (72 percent) of patients [51]. Mechanical cervical dilatation prior to D&E was required for the remaining 28 percent of patients in whom dilation was not adequate.

A variation of this procedure, where the balloon catheter is attached to a small weight (eg, 1 L of fluid), may further hasten this process.

Mifepristone — Mifepristone is an antiprogesterone that softens the cervix and aids in dilation when administered 18 to 24 hours prior to D&E. This is in contrast to misoprostol, which is given a few hours before procedural abortion. Mifepristone has the advantage of not causing significant gastrointestinal side effects or cramping, in contrast with misoprostol.

Mifepristone is used in terminations ≥18 weeks along with osmotic dilators since the combination results in less difficult dilation; shorter procedure time; and the need for one, rather than two, nights of dilators when compared with dilators alone [16]. It may also be used in combination with misoprostol (table 1). (See '≥18 weeks' above and 'Two-day protocol' above.)

Due to its antiglucocorticoid properties, mifepristone should not be used by patients on long-term systemic steroids [27].

Other — Ulipristal acetate, a selective progesterone receptor modulator, is more widely available than mifepristone in some settings, and may be effective for cervical preparation when used as an adjunct to misoprostol [52]. Further studies are needed before ulipristal can be used for this indication.

ROLE OF MECHANICAL DILATION — Mechanical dilation is performed immediately prior to procedural abortion using Hegar, Pratt, Denniston, Hanks, or other types of rigid dilators (picture 3 and figure 1). In second-trimester D&E, mechanical dilation is typically used only after cervical preparation with misoprostol, mifepristone, osmotic dilators, or a combination of these measures; however, mechanical dilation is often used alone for first-trimester procedures.

Risks of mechanical dilation include cervical laceration and uterine perforation. A false passage can be created by inserting the dilator into the cervical stroma rather than the os. This increases the chance of a cervical or uterine perforation. The risk is increased in patients with a prior cesarean birth since scar tissue may be present and may affect the angle of the cervical canal [53]. Ultrasound may be used during the procedure to guide insertion and avoid uterine perforation. (See "Uterine perforation during gynecologic procedures", section on 'Prevention'.)

The incidence of complications associated with mechanical dilation is low but is reduced by additional cervical preparation. As an example, in a large retrospective study of nearly 12,000 second-trimester D&E procedures, use of rigid dilation alone was associated with a higher incidence of cervical laceration, especially at later gestational ages: mechanical dilation alone (laceration rates: 0.8 to 0.9 percent at 13 to 17 weeks; 5 to 8 percent at 18 to 21 weeks) versus laminaria use (0 to 0.6 percent at 13 to 17 weeks; 1.4 to 1.6 percent at 18 to 21 weeks) [1].

SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Pregnancy termination".)

INFORMATION FOR PATIENTS — UpToDate offers two types of patient education materials, "The Basics" and "Beyond the Basics." The Basics patient education pieces are written in plain language, at the 5^th to 6^th grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are written at the 10^th to 12^th grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon.

Here are the patient education articles that are relevant to this topic. We encourage you to print or e-mail these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on "patient info" and the keyword(s) of interest.)

●Basics topics (see "Patient education: Abortion (The Basics)")

●Beyond the Basics topics (see "Patient education: Abortion (pregnancy termination) (Beyond the Basics)")

SUMMARY AND RECOMMENDATIONS

●Clinical significance – Cervical preparation is often used to soften and dilate the cervix prior to procedures for pregnancy termination. The aims are to decrease cervical trauma from mechanical dilation and to facilitate the evacuation of the uterus. (See 'Introduction' above.)

●Types of dilators and medications

•Osmotic dilators – Osmotic dilators are rod-shaped items that are placed in the cervical os and dilate gradually as they absorb moisture (picture 1 and picture 2). They are placed from four hours up to two days prior to the procedure, depending on the type of osmotic dilator used, the degree of dilation required, and whether a cervical ripening medication is used concomitantly. (See 'Osmotic dilators' above.)

•Cervical ripening medications – Cervical ripening agents, including misoprostol (a prostaglandin E1 analog) and mifepristone (an antiprogesterone), are medications that help to soften the cervix and make it easier to dilate with osmotic or mechanical dilators. Misoprostol, if used, is administered on the day of the procedure. Potential side effects include gastrointestinal upset, vomiting, cramping, or vaginal bleeding. Mifepristone, if used, is administered on the day before the procedure and has the advantage of not causing significant gastrointestinal side effects or cramping. (See 'Cervical ripening medications' above.)

•Mechanical dilators – Mechanical dilation with rigid dilators (figure 1 and picture 3) is often used alone for procedural abortions <12 weeks but typically used only after cervical preparation (with misoprostol, mifepristone, osmotic dilators, or a combination of these measures) in procedural abortions performed ≥12 weeks. (See 'Role of mechanical dilation' above.)

●Approach by gestational age – The key determinant to our approach to cervical preparation is gestational age. Other factors that guide the approach include a history of cesarean birth or cervical surgery, uterine anomalies, or fetal anomalies that result in an increased biparietal diameter. (See 'Approach by gestational age' above and 'Special circumstances' above.)

•<12 weeks of gestation – We recommend not using cervical preparation (Grade 1B). Typically, mechanical dilation with rigid dilators alone is safe and effective. (See '<12 weeks' above.)

•12 to <14 weeks of gestation – Patients who are nulliparous, ≤17 years of age, or have barriers to dilation (eg, history of cervical surgery, cervical stenosis, cervical fibroids) may have an increased risk of cervical injury with mechanical cervical dilation. For these high-risk patients, we suggest using cervical preparation (Grade 2C). Either misoprostol or overnight osmotic dilators are acceptable options (table 1). Some clinics also use cervical preparation in low-risk patients ≥12 weeks, including multiparous patients. (See '12 to <14 weeks' above.)

•14 to <18 weeks of gestation – We suggest using cervical preparation for essentially all such patients (Grade 2C). The exceptions are clinical situations in which cervical preparation is not feasible and an experienced provider determines that proceeding without preparation is appropriate. Same-day and two-day protocols have similar efficacy and safety profiles, and the type of cervical preparation is based primarily on patient preference and clinic resources (table 1). (See '14 to <18 weeks' above.)

•≥18 weeks of gestation – We recommend using cervical preparation for essentially all such patients (Grade 1B). A variety of different protocols are available: some using overnight dilators alone and others using overnight dilators with mifepristone or misoprostol (table 1). All are acceptable options and depend largely on clinic resources and provider preference. At 20 to 24 weeks of gestation, one frequently used protocol is the combination of mifepristone and overnight osmotic dilators. Misoprostol can also be used on the day of the procedure to further increase cervical dilation. (See '≥18 weeks' above.)

●Preprocedure medications – For analgesia, we administer 600 to 800 mg ibuprofen approximately 30 minutes before and a paracervical block immediately before osmotic dilator placement. To decrease risk of infection, we give one dose of azithromycin 500 mg orally at the time of dilator placement. Given its long half-life, a second dose is not needed prior to the procedural abortion if performed within 24 hours of the initial dose of antibiotics (table 3). Other providers defer antibiotics at the time of dilator placement and rather administer antibiotics only preoperatively. (See 'Procedure' above.)