Cervical priming before surgical abortion between 14 and 24 weeks: a systematic review and meta-analyses for the National Institute for Health and Care Excellence-new clinical guidelines for England

Abstract

Objective: This study aimed to determine the optimal cervical priming regimen before surgical abortion between 14⁺⁰ and 24⁺⁰ weeks' gestation.

Data sources: Embase, MEDLINE, and the Cochrane Library were searched for publications up to February 2020. Experts were consulted for any ongoing or missed trials.

Study eligibility criteria: Randomized controlled trials, published in English after 1985, that compared (1) mifepristone, misoprostol, and osmotic dilators against each other, alone or in combination; (2) different doses of mifepristone and misoprostol; (3) different intervals between priming and abortion; or (4) different routes of administration of misoprostol were included.

Methods: Risk of bias was assessed using the Cochrane Collaboration checklist for randomized controlled trials, and data were meta-analyzed in Review Manager 5.3. Dichotomous outcomes were analyzed as risk ratios using the Mantel-Haenszel method, and continuous outcomes were analyzed as mean differences using the inverse variance method. Fixed effects models were used when there was no significant heterogeneity (I²<50%), random effects models were used for moderate heterogeneity (I²≤50% and <80%), and evidence was not pooled when there was high heterogeneity (I²≥80%). Subgroup analyses were undertaken based on parity where available. The overall quality of the evidence was assessed using Grades of Recommendation Assessment, Development, and Evaluation.

Results: A total of 15 randomized controlled trials (N=2454) were included and showed decreased difficulty of procedure and/or increased cervical dilation and decreased patient acceptability with regimens that included dilators compared with those that did not include dilators; increased preoperative expulsion of the pregnancy with sublingual misoprostol and mifepristone compared with sublingual misoprostol alone; increased difficulty of procedure with dilators and misoprostol compared with dilators and mifepristone; decreased difficulty of procedure with dilators and mifepristone compared with dilators alone; and increased cervical dilation when dilators were placed the day before abortion compared with the same day.

Conclusion: Considered alongside clinical expertise, the published data support the use of osmotic dilators, misoprostol, or mifepristone before abortion for pregnancies at 14⁺⁰ to 16⁺⁰ weeks' gestation; osmotic dilators or misoprostol for pregnancies at 16⁺¹ to 19⁺⁰ weeks' gestation; and osmotic dilators alone or with mifepristone for pregnancies at 19⁺¹ to 24⁺⁰ weeks' gestation. The effectiveness of pharmacologic agents alone beyond 16⁺⁰ weeks' gestation and the optimal timing of dilator placement remain important questions for future research.

Keywords: Dilapan; cervical priming; dilation and evacuation; laminaria; mifepristone; misoprostol; osmotic dilators; second trimester; surgical abortion; vacuum aspiration.