Background: Cervical preparation prior to dilation and evacuation reduces the risk of rare complications including uterine perforation and cervical laceration. Yet, a single best approach to cervical preparation before second trimester surgical abortion does not exist. The predictability of cervical dilation is important in some settings, especially when operating room time has been scheduled and reserved. Occasionally, additional cervical preparation may be required to complete the procedure. A better understanding of how the predictability and need for additional cervical preparation varies by method will provide clinicians with useful, patient-centered evidence for their practice.
Statement of purpose: We sought to examine the predictability of cervical preparation methods using individual participant data meta-analysis methodology.  
Methodology: We conducted a systematic review and individual participant data meta-analysis of randomized controlled trials that compared cervical preparation prior to surgical abortion between 14w0d and 24w0d. The cervical preparation methods compared included overnight dilators and pharmacologic-only methods including mifepristone alone, mifepristone then misoprostol and misoprostol alone. Our primary objective was to determine the association between initial cervical preparation method and the need for misoprostol to achieve adequate cervical preparation before dilation and evacuation between 14w0d and 24w0d.
Important findings: We obtained participant level data from 8 studies or 541 participants. The need for additional cervical preparation with misoprostol occurred in 16% (37/226) of participants receiving pharmacologic-only methods of cervical preparation. This finding is limited in the all participants receiving additional cervical preparation were from a single study.
Summary Statement: Pharmacologic-only methods of cervical preparation are associated with increased need for additional misoprostol but overall most women do not need additional cervical preparation prior to dilation and evacuation. Although rare, delayed procedures are a meaningful and patient-centered outcome to consider when selecting a cervical preparation method.