For a dilation and evacuation (D&E) procedure, the cervix must be dilated sufficiently to allow passage of operative instruments and products of conception without injuring the uterus or cervical canal. Preoperative preparation of the cervix reduces the risk of cervical laceration and uterine perforation. The cervix may be prepared with osmotic dilators, pharmacologic agents or both. Dilapan-S™ and laminaria are the two osmotic dilators currently available in the United States. Laminaria tents, made from dehydrated seaweed, require 12-24 h to achieve maximum dilation. Dilapan-S™, made of synthetic hydrogel, achieves significant dilation within 4 h and is thus preferable for same-day procedures. A single set of one to several dilators is usually adequate for D&E before 20 weeks\' gestation. Misoprostol, a prostaglandin E1 analogue, is sometimes used instead of osmotic dilators. It is generally regarded as safe and effective; however, misoprostol achieves less dilation than overnight osmotic tents. The literature supports same-day cervical preparation with misoprostol or Dilapan-S™ up to 18 weeks\' gestation. As the evidence regarding alternative regimens increases, highly experienced D&E providers may consider same-day regimens at later gestations utilizing serial doses of misoprostol or a combination of osmotic and pharmacologic agents. Misoprostol use as an adjunct to overnight osmotic dilation is not significantly beneficial before 19 weeks\' gestation. Limited data demonstrate the safety of misoprostol before D&E in patients with a prior cesarean delivery. Mifepristone, a progesterone receptor antagonist, is also effective for cervical preparation prior to D&E, although data to support its use are limited. The Society of Family Planning recommends preoperative cervical preparation to decrease the risk of complications when performing a D&E. Since no single protocol has been found to be superior in all situations, clinical judgment is warranted when selecting a method of cervical preparation.

First-trimester surgical abortion is a common, safe procedure with a major complication rate of less than 1%. Cervical dilation before suction aspiration is usually accomplished using tapered mechanical dilators. Risk factors for major complications in the first trimester are increasing gestational age and provider inexperience. Use of laminaria for cervical priming reduces the risk of cervical laceration and, to a lesser extent, uterine perforation. While pharmacological priming agents may potentially have the same effects, no published studies to date have been large enough to assess these outcomes. Given an experienced provider, the risk of these injuries during suction aspiration is very small. Cervical priming can be achieved with osmotic dilators or pharmacological agents. The advantages of osmotic dilators such as laminaria, Dilapan-S and Lamicel are their ability to produce wide cervical dilation, and for the synthetic types, their advantages include predictable effects and rapid onset of action. A disadvantage of osmotic dilators is that they require a speculum examination and a trained clinician to perform the insertion. When cervical priming is performed, misoprostol is the prostaglandin analogue most commonly used worldwide. Compared to laminaria, vaginal misoprostol requires a shorter period of time to achieve the same dilatation, is associated with less discomfort and is preferred by women. The sublingual route appears as effective as vaginal administration and requires less time for priming (2 h), but it is associated with more side effects. Oral administration can produce equivalent dilation to vaginal or sublingual administration, but higher doses and longer treatment periods (8 to 12 h) are required. Buccal administration of misoprostol appears to have a pharmacokinetic and physiologic profile similar to vaginal administration; however, there are no published studies of buccal misoprostol prior to first-trimester suction abortion. While extensive data demonstrate that a variety of agents are safe and effective at causing cervical softening and dilation preoperatively, there are not enough data to conclude that routine cervical priming is necessary to reduce complications of first-trimester surgical abortion. Cervical priming increases preoperative cervical dilation, making the procedure easier and quicker for the physician. However, in order to preoperatively dilate the cervix, the woman must receive the agent at least 3 to 4 h prior to her procedure. Besides the additional waiting, the woman might experience bleeding and cramping prior to the procedure. There are insufficient data evaluating how cervical priming affects women\'s quality of life in relation to abortion. Based on existing evidence, the Society of Family Planning does not recommend routine cervical priming for suction aspiration procedures. The Society of Family Planning further recommends that providers consider cervical priming only for women who may be at increased risk of complications from cervical dilation, including those late in the first trimester, adolescents and women in whom cervical dilation is expected to be difficult due to either patient factors or provider experience.