Objectives: To describe leukocytosis trends during cervical preparation with osmotic dilators for second-trimester dilation and evacuation procedures, and to determine whether there is a difference in leukocytosis seen with laminaria versus Dilapan-S. Methods: We conducted a retrospective cohort study of 986 women presenting for dilation and evacuation from April 2008 through March 2009 at an outpatient clinic network. We included all procedures at ⩾14 weeks’ gestation where laminaria or Dilapan-S dilators were used for overnight dilation. All women had routine white blood cell testing during the study period. Results: There was a median increase of 2.4 × 103/μL white blood cell count (95% confidence interval 2.2–2.7 × 103/μL) from beginning of cervical preparation to the day of procedure (95% confidence interval and p value). Women receiving laminaria ( n = 805) versus Dilapan-S ( n = 181) had a greater increase in white blood cell count from baseline (median increase 2.7 versus 1.2 × 103/μL, p < 0.001), including when adjusting for age, gestational age, parity, baseline white blood cell count, and number of dilators placed. Conclusion: There is increased leukocytosis during the course of cervical preparation with osmotic dilators, and this is increased with use of laminaria versus Dilapan-S. Rates of clinically recognized infection in second-trimester abortion are low regardless of dilator type used.