Key messages
• Prostaglandin and osmotic dilators are likely safe and effective methods of cervical priming agents before second trimester surgical abortion.
• Misoprostol plus osmotic dilators probably increases pre-procedure cervical dilation and reduces procedure time and need for additional dilation compared to placebo (dummy treatment) plus osmotic dilators.
• Overnight laminaria may improve procedure time, pre-procedure dilation, and need for additional dilation compared to same-day Dilapan-S.
• Future studies should be larger and look at Foley catheters as a method of cervical priming for second-trimester surgical abortion.
Why is this question important?
Pregnant people prefer to have options to choose for their pregnancy termination, that is medical abortion versus surgical abortion using dilation and evacuation (D&E, a procedure that opens the cervix so tissue in the uterus can be removed using an instrument). Most providers use cervical priming agents prior to second trimester uterine surgical evacuation. Commonly used medical methods for cervical preparation are prostaglandins (misoprostol) and an antiprogesterone (mifepristone). Mechanical methods of cervical priming include osmotic dilators (laminaria and Dilapan-S). Providers may use medicine or mechanical methods, or both, based on different factors, including gestational age. There is no agreement on the best method of cervical priming agent used before D&E.
What did we do?
We searched for studies comparing the effects of different forms of cervical priming agents used before second trimester surgical abortion. We compared and summarized the results and rated our confidence in the evidence based on factors such as study methods and sizes.
What did we find?
We found 21 studies involving 3029 participants. Few studies compared the same two cervical priming agents. Mifepristone was taken 24 to 48 hours prior to misoprostol or osmotic dilators, except in one study where it was used at the same time as laminaria. Mifepristone was used at a dose of 200 mg and misoprostol at a dose of 400 to 600 μg.
Prostaglandin versus osmotic dilators
Prostaglandin may have little to no effect on procedure time, but probably leads to less dilation achieved compared with osmotic dilators.
Mifepristone plus misoprostol versus osmotic dilators
Mifepristone plus misoprostol may have little to no effect on procedure time, but it may lead to less dilation achieved and an increased need for additional dilation and have little to no effect on ability to complete procedure compared with osmotic dilators.
Misoprostol plus osmotic dilators versus placebo plus osmotic dilators
Misoprostol plus osmotic dilators probably reduces procedure time; increases dilation achieved; reduces need for additional dilation; and has little to no effect on ability to complete procedure compared with placebo plus osmotic dilators.
Mifepristone plus osmotic dilators versus placebo plus osmotic dilators
Mifepristone plus osmotic dilators may reduce procedure time, and probably increases dilation achieved compared with placebo plus osmotic dilators. Mifepristone plus osmotic dilators may have little to no effect on need for additional dilation, but there is probably little to no effect on ability to complete procedure.
Misoprostol plus osmotic dilators versus mifepristone plus osmotic dilators
Misoprostol plus osmotic dilators may have little to no effect on procedure time, dilation achieved, and need for additional dilation compared with mifepristone plus osmotic dilators. There is probably little to no difference in ability to complete procedure.
Mifepristone plus misoprostol plus dilators compared to misoprostol plus osmotic dilators
Mifepristone plus misoprostol plus osmotic dilators may have little to no effect on procedure time, dilation achieved, and need for additional dilation compared with misoprostol plus osmotic dilators. Ability to complete procedure was not reported.
Misoprostol plus osmotic dilators versus misoprostol
Misoprostol plus osmotic dilators probably increases procedure time (if procedure time includes the time elapsed for insertion of osmotic dilators); increases dilation achieved; reduces the need for additional dilation; and has little to no effect on ability to complete procedure compared with misoprostol alone.
Laminaria versus synthetic osmotic dilators
It is uncertain if laminaria has any effect on procedure time, but probably makes little to no difference in dilation achieved, and may reduce ability to complete procedure compared with synthetic osmotic dilators.
Same-day Dilapan-S versus overnight laminaria
Same-day Dilapan-S may increase procedure time; reduce dilation achieved; and increase need for additional dilation compared with overnight laminaria. There may be little to no difference in ability to complete procedure between groups.
What are the limitations of the evidence?
We have only moderate to little confidence in the evidence because of differences in the size or direction of effect and few people contributing data to the analyses. More studies are needed to increase our confidence in the evidence.
How up-to-date is this review?
The evidence is current to 20 December 2021.
We identified a heterogeneous body of evidence comparing different cervical priming approaches. Compared with osmotic dilators plus placebo, misoprostol plus osmotic dilators probably reduces procedure time, increases pre-procedure cervical dilation, and reduces the number of people who need additional dilation. Compared with osmotic dilators plus placebo, mifepristone plus osmotic dilators may reduce procedure time and probably increases pre-procedure cervical dilation. Overnight laminaria may reduce procedure time, increase pre-procedure dilation, and reduce need for additional dilation compared to same-day Dilapan-S.
Further studies are needed that focus on both provider and patient acceptability and satisfaction.
Abortion is a common procedure. Complications associated with abortion increase as gestational age increases. Cervical preparation is recommended prior to second trimester surgical abortion. Evidence is lacking as to the most effective methods of cervical preparation.
To assess the effectiveness of cervical preparation methods for people undergoing second trimester surgical abortion at gestational age between 12 and 24 0/7 weeks.
We searched CENTRAL, MEDLINE ALL, Embase.com, Global Index Medicus, Scopus, and Google Scholar on 20 December 2021. We also searched reference lists, review articles, books, and conference proceedings. We contacted experts for information on other published or unpublished research. The COVID-19 pandemic greatly disrupted the writing and publication of this review; the search is outdated, but an updated search will be performed prior to the next update.
We included randomized controlled trials (RCTs) investigating any cervical preparation method for second trimester surgical abortion from 12 to 24 weeks gestation.
We used standard Cochrane methods.
We identified 21 RCTs (3029 participants). Some trials were at high risk of detection and reporting bias.
Prostaglandin versus osmotic dilators (4 studies, 373 participants; 12 6/7 to 20 weeks)
Prostaglandin may result in little to no difference in ability to complete procedure (risk ratio [RR] 0.99, 95% confidence interval [CI] 0.95 to 1.03; low-certainty evidence), but probably leads to less dilation achieved (mean difference [MD] −3.58 mm, 95% CI −4.58 to −2.58; moderate-certainty evidence) when compared to osmotic dilators.
Mifepristone plus 400 μg buccal misoprostol versus osmotic dilators (1 study, 49 participants; 15 0/7 to 18 0/7 weeks)
Mifepristone plus misoprostol may have little to no effect on ability to complete procedure (RR 1.00, 95% CI 0.92 to 1.08; low-certainty evidence) and procedure time (MD −0.30, 95% CI −3.46 to 2.86) when compared to osmotic dilators. The combination may lead to less dilation achieved (MD −1.67 mm, 95% CI −3.19 to −0.15; low-certainty evidence) and increased need for additional dilation (RR 1.92, 95% CI 1.16 to 3.18; low-certainty evidence) compared to osmotic dilators.
400 μg buccal misoprostol plus osmotic dilators versus placebo plus osmotic dilators (4 studies, 545 participants; 13 to 23 6/7 weeks)
Misoprostol plus osmotic dilators probably has no effect on ability to complete procedure (RR 0.99, 95% CI 0.96 to 1.02; moderate-certainty evidence), but probably increases dilation achieved (MD 1.83 mm, 95% CI 0.27 to 3.39; moderate-certainty evidence) and reduces need for additional dilation (RR 0.65, 95% CI 0.50 to 0.84; moderate-certainty evidence) and procedure time (MD −0.99 min, 95% CI −2.05 to 0.06; moderate-certainty evidence) compared to placebo plus osmotic dilators.
Mifepristone plus osmotic dilators versus placebo plus osmotic dilators (1 study, 198 participants; 16 0/7 to 23 6/7 weeks)
Mifepristone plus osmotic dilators probably has little to no effect on ability to complete procedure when compared to placebo plus osmotic dilators (RR 1.00, 95% CI 0.97 to 1.03; moderate-certainty evidence). Mifepristone plus osmotic dilators may reduce procedure time (2.46 min shorter: median, interquartile range, 9.12 min, 7.7 to 10.6; compared to 11.58 minutes, 10.0 to 13.1; low-certainty evidence) and probably increases dilation achieved (MD 2.00 mm, 95% CI 0.60 to 3.40; moderate-certainty evidence). There appears to be no effect on need for additional dilation.
400 μg buccal misoprostol plus osmotic dilators versus mifepristone plus osmotic dilators (1 study, 199 participants; 16 0/7 to 23 6/7 weeks)
There is likely no difference in ability to complete procedure between groups (RR 0.99, 95% CI 0.96 to 1.02; moderate-certainty evidence). Misoprostol plus osmotic dilators does not appear to affect procedure time, dilation achieved, and need for additional dilation compared with mifepristone plus osmotic dilators.
Mifepristone plus 400 μg buccal misoprostol plus osmotic dilators compared to 400 μg buccal misoprostol plus osmotic dilators (1 study, 96 participants; 19 to 23 6/7 weeks)
Mifepristone plus misoprostol plus osmotic dilators may have little to no effect on procedure time, dilation achieved, or need for additional dilation compared with misoprostol plus osmotic dilators.
400 μg buccal or vaginal misoprostol plus osmotic dilators versus 400 μg buccal or vaginal misoprostol (1 study, 163 participants; 14 to 19 6/7 weeks)
There is probably no difference between groups in ability to complete procedure (RR 1.00, 95% CI 0.98 to 1.02; moderate-certainty evidence). Misoprostol plus osmotic dilators likely increases dilation (MD 3.9 mm, 95% CI 3.1 to 4.7; moderate-certainty evidence) and reduces need for additional dilation (RR 0.77, 95% CI 0.63 to 0.93; moderate-certainty evidence).
Laminaria versus synthetic osmotic dilators (1 study, 219 participants; 13 6/7 to 24 0/7 weeks)
Laminaria japonica may reduce ability to complete procedure at first attempt compared with synthetic osmotic dilators (RR 0.85, 95% CI 0.75 to 0.96; low-certainty evidence). It is uncertain if there is a difference in procedure time between groups. Laminaria likely does not effect dilation achieved (RR 1.0, 95% CI 0.8 to 1.3; moderate-certainty evidence).
Same-day Dilapan-S versus overnight laminaria (1 study, 69 participants; 13 6/7 to 17 6/7 weeks)
Same-day Dilapan-S may increase procedure time (MD 2.20 min, 95% CI 0.10 to 4.30; low-certainty evidence); reduce dilation achieved (MD −11.70 mm, 95% CI −16.74 to −6.66; low-certainty evidence); and increase need for additional dilation (RR 2.83, 95% CI 1.47 to 5.46; low-certainty evidence) compared with laminaria. There appears to be no difference in ability to complete procedure.