Iranian Society of Gynecology Oncology


1 Gynocologist, Iran University of Medical Sciences, Akbarabady Hospital, Tehran, Iran

2 Social Medicine Specialist, Iran University of Medical Sciences, Tehran, Iran

3 Department of Obstetrics and Gynecolgy, Iran University of Medical Sciences, Tehran, Iran


Background: Vaginal misoprostol is said to dissolve better in an acidic environment, thus, in this study we aimed to evaluate the influence of increasing vaginal acidity on the effectiveness of vaginal misoprostol for the induction of midtrimester pregnancy using acidic environment.
Methods: A total of 40 women requiring second trimester pregnancy termination were randomly assigned to one of two treatment groups: (A) in the saline group, 400 µg of intra-vaginal misoprostol was moistened in normal saline before the vaginal insertion as controls (n = 20); and (B) in the acetic acid group, the acidity of the vagina was increased with 3% of acetic acid, (4 mL of 3% acetic acid was delivered into the vagina every 6 hours) before the insertion of an initial dose of 400 µg misoprostol (n = 20). Then 200 µg dosage was repeated every 4 hours for a maximum of 5 doses within 24 hours. If the patient did not have adequate uterine contractions, the same regimen was repeated over the following 24 hours and if no response was achieved, this was considered a failure of therapy.
Results: There was no significant difference in the vaginal pH between the control and intervention groups before the vaginal application of acetic acid (5.80 ± 0.62 versus 5.89 ± 0.49, P = 0.622,). The vaginal pH was significantly lower in the acetic acid group after the vaginal application of acetic acid compared to the control group (5.11 ± 0.56 versus 5.80 ± 0.62, P = 0.001). Overall, 95% of pregnancies were successfully terminated in the acetic acid group compared to 85% in the control group. These differences were not statistically significant (P =0.241). The success rate within 24 hours and 48 hours, the adverse effects, mean termination time, total misoprostol administered, and the number of curettage were, also, comparable between the two groups.
Conclusions: Findings from this study shows that increasing Vaginal acidity does not improve the efficacy of misoprostol administered intra-vaginally for the second trimester pregnancy termination.


  1. Rivlin M. E. , Martin R. W. . Manual of Clinical Problems in Obstetrics and Gynecology. 5th edition ed. ; 1997. pp. 117-22.
  2. Cunningham FG, Leveno KJ, Bloom SL, Spong CY, Dashe JS, Hoffman BL, et al. Williams Obstetrics. 24th edition ed. McGraw-Hill Education; 2014. pp. 725-8.
  3. Owen J, Hauth JC, Winkler CL, Gray SE. Midtrimester pregnancy termination: A randomized trial of prostaglandin E2 versus concentrated oxytocin. American Journal of Obstetrics and Gynecology. 1992;167(4):1112-6. [DOI:10.1016/S0002-9378(12)80049-4]
  4. Herabutya Y, O-Prasertsawat P. Second trimester abortion using intravaginal misoprostol. International Journal of Gynecology & Obstetrics. 1998;60(2):161-5. [DOI:10.1016/S0020-7292(97)00244-0]
  5. Singh K, Fong YF, Prasad RN, Dong F. Does an acidic medium enhance the efficacy of vaginal misoprostol for pre-abortion cervical priming? Hum Reprod. 1999;14(6):1635-7. [DOI:10.1093/humrep/14.6.1635] [PMID]
  6. Ramsey PS, Ogburn PJ, Harris DY, Heise RH, Ramin KD. Effect of vaginal pH on efficacy of misoprostol for cervical ripening and labor induction. Am J Obstet Gynecol. 2000;182(6):1616-9. [DOI:10.1067/mob.2000.107441] [PMID]
  7. Singh U, Mehrotra S, Gupta HP, Dhakad A, Jain V. A prospective double blind trial investigating impact of vaginal pH on efficacy of prostaglandin gel for cervical ripening and course of labour. J Obstet Gynaecol. 2011;31(3):217-9. [DOI:10.3109/01443615.2010.546905] [PMID]
  8. Chandra S, Allen V, Lee W, Fanning C, Young D. The effect of vaginal pH on labor induction with vaginal misoprostol. J Matern Fetal Neonatal Med. 2005;17(6):387-91. [DOI:10.1080/14767050500123863] [PMID]
  9. Pongsatha S, Tongsong T. Randomized controlled study comparing misoprostol moistened with normal saline and with acetic acid for second-trimester pregnancy termination. Is it different? J Obstet Gynaecol Res. 2011;37(7):882-6. [DOI:10.1111/j.1447-0756.2010.01458.x] [PMID]
  10. Bhattacharjee N, Saha SP, Ganguly RP, Patra KK, Jha T, Barui G, et al. A randomized comparative study on vaginal administration of acetic acid-moistened versus dry misoprostol for mid-trimester pregnancy termination. Arch Gynecol Obstet. 2012;285(2):311-6. [DOI:10.1007/s00404-011-1949-z] [PMID]
  11. Abd-El-Maeboud KH, Ghazy AA, Nadeem AA, Al-Sharaky A, Khalil AE. Effect of vaginal pH on the efficacy of vaginal misoprostol for induction of midtrimester abortion. J Obstet Gynaecol Res. 2008;34(1):78-84.
  12. Yilmaz B, Ertas IE, Kelekci S, Sut N, Mollamahmutoglu L, Danisman N. Moistening of misoprostol tablets with acetic acid prior to vaginal administration for mid-trimester termination of anomalous pregnancy: A randomised comparison of three regimens. Eur J Contracept Reprod Health Care. 2010;15(1):54-9. [DOI:10.3109/13625180903417486] [PMID]
  13. Herabutya Y, O. Prasertsawat P . Mid-trimester abortion using hypertonic saline or prostaglandin E2 gel: an analysis of efficacy and complications. J Med Assoc Thai. 1994;77(3):148-52.
  14. Srisomboon J, Tongsong T, Pongpisuttinun S. Termination of secondtrimester pregnancy with intracervicovaginal misoprostol. J Med Assoc Thai. 1997;80(4):242-6.