Objective: To determine the optimal dosage of vaginal misoprostol for cervical priming before vacuum aspiration abortion.
Methods: One hundred twenty women were assigned randomly to receive 200, 400, 600, or 800 microg of misoprostol given vaginally. Vacuum aspiration was performed 3-4 hours after the insertion of misoprostol tablets. The degree of cervical dilation before operation was measured with a Hegar dilator. Preoperative and intraoperative blood loss and associated side effects also were assessed.
Results: Twenty-nine (96.7%) women in the 400-microg group and all in the 600-microg and 800-microg groups achieved cervical dilation of at least 8 mm. The success rate for the 200-microg group was only 23.3%, significantly less efficacious than the 400-microg dose (odds ratio 95.3; 95% confidence interval 10.9, 830.9; P < .001). There was no significant difference among the 400-, 600-, and 800-microg groups (P = .364) with respect to achieving cervical dilation at least 8 mm. However, 800 microg was associated with significantly more side effects than 600 microg (preoperative and intraoperative blood loss, P < .001; abdominal pain, P = .005; products of conception at os, P < .001; fever higher than 38.0C, P = .002). When 400 microg and 600 microg were compared, we found that the higher dose also was associated with significantly more side effects. The 600-microg group was used twice in the comparison, but all P values remained significant even after the Bonferroni adjustment for multiple comparisons.
Conclusion: Vaginal application of 400 microg of misoprostol is the optimal dose for vacuum aspiration preabortion cervical dilation in first-trimester nulliparas.