Cervical preparation for dilation and evacuation at 12 to 24 weeks gestation.

Background: 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.

Objectives: 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.

Search Methods: 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 We contacted experts for information on other published or unpublished research. The COVID-19 pandemic greatly disrupted the writing and publication of this review; the search is outdated, but an updated search will be performed prior to the next update.

Selection Criteria: We included randomized controlled trials (RCTs) investigating any cervical preparation method for second trimester surgical abortion from 12 to 24 weeks gestation.

Data Collection And Analysis: We used standard Cochrane methods.

Main Results: 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.

Authors' Conclusions: 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.