The effect of vaginal evening primrose capsule on cervical ripening in nulliparous women with post-term pregnancy: A clinical trial

Document Type : Original Article


1 Assistant Professor, Department of Reproductive Health and Midwifery, School of Medical Sciences, Tarbiat Modares University, Tehran, Iran.

2 M.Sc. student of Midwifery, Reproductive Health Promotion Research Center, School of Nursing and Midwifery, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran.

3 PhD in Reproductive health, Reproductive Health promotion Research Center, School of Nursing and Midwifery, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran.

4 Assistant Professor, Department of Epidemiology and Biostatistics, School of Public Health, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran.


Introduction: post term pregnancy is associated with maternal and fetal complications, including sudden death of the fetus and low Apgar score after birth. Evening primrose oil has been used for cervical ripening. Despite the effects of evening primrose oil on prostaglandin precursor levels and the well-established role of prostaglandins in the reconstruction of cervical matrix. This study was performed with aim to evaluate the effect of vaginal consumption of evening primrose oil on cervical ripening in nulliparous women with post-term pregnancy.
Methods: This randomized clinical trial study was conducted on 60 pregnant women with post-term pregnancy who referred to the maternity of Ahvaz Sina Hospital in 2017. The study groups consisted of 2 groups: vaginal capsule of 1000 mg of evening primrose oil and placebo. Drug was administered after induction of labor with 10 unit oxytocin. In the intervention group, one vaginal capsule of 1000 mg of evening primrose oil and in the control group, gelatin capsule as similar as the drug were used. Then, the induction of labor was started with oxytocin with similar dose (10 unit in 1000 cc serum ringer) in both groups. Cervical ripening was measured based on regular examination (every one hour). Data were collected by demographic questionnaire, timing, and bishop-score checklist. Data were analyzed by SPSS software (version 22) and independent t-test and Chi-square test. P<0.05 was considered statistically significant.
Results: The duration of the latent phase in both groups was 9-10.5 hour. The duration of latent phase (p=0.003) and bishop score (p=0.01) had significant difference between the intervention group and the placebo group; it means more cervical ripening in the intervention group. At second stage of measurement, bishop score ≥7 was 90% in the intervention group and 60% in the control group that was significantly more in the intervention group (P=0.01). However, no significant difference between the two groups in terms of the duration of the active phase, progression rate, severity of pain, and volume of bleeding.
Conclusion: The vaginal use of evening primrose oil reduces the duration of the latent phase and has a positive effect on the cervical ripening and Bishop score.


  1. American College of Obstetricians and Gynecologists. Practice bulletin no. 146: management of late-term and postterm pregnancies. Obstet Gynecol 2014; 124:390-6.
  2. Gibbs RS, Danforth DN. Danforth's obstetrics and gynecology. 10th ed. Philadelphia: Lippincott Williams & Wilkins; 2008.
  3. Maul H, Mackag L, Garfield RE. Cervical ripening: biochemical, molecular, and clinical considerations. Clin Obstet Gynecol 2006; 49(3):551-63.
  4. Timmons BC, Manendroo M. Processes regulating cervical ripening differ from cervical dilation and post partum repair: insights from gene expression studies. Report Sci 2007; 14(8 Suppl):53-62.
  5. Harman JH Jr, Kim A. Current trends in cervical ripening and labor induction. Am Fam Physician 1999; 60(2):477-84.
  6. Kernoff PB, Willis AL, Stone KJ, Davies JA, McNicol GP. Antithrombotic potential of dihomo-gamma-linolenic acid in man. Br Med J 1977; 2(6100):1441-4.
  7. PonMalar J, Benjamin SJ, Abraham A, Rathore S, Jeyaseelan V, Mathews JE. Randomized double-blind placebo controlled study of preinduction cervical priming with 25 µg of misoprostol in the outpatient setting to prevent formal induction of labour. Arch Gynecol Obstet 2017; 295(1):33-8.
  8. Luria O, Jaffa A, Farine D, Hassan S, Lysikiewicz A, Kees S, et al. Effects of the individual uterine contraction on fetal head descent and cervical dilatation during the active stage of labor. Eur J Obstet Gynecol Reprod Biol 2009; 144(Suppl 1):S101-7.
  9. Polit FD, Beck CT. Study guide for essentials of nursing research. 9th ed. Philadelphia: Lippincott Williams & Wilkins; 2013.
  10. Crane JM. Factors predicting labor induction success: a critical analysis. Clin Obstet Gynecol 2006; 49(3):573-84.
  11. Teixeira C, Lunet N, Rodrigues T, Barros H. The Bishop Score as a determinant of labour induction success: a systematic review and meta-analysis. Arch Gynecol Obstet 2012; 286(3):739-53.
  12. Grobman WA, Simon C. Factors associated with the length of the latent phase during labor induction. Eur J Obstet Gynecol Reprod Biol 2007; 132(2):163-6.
  13. Sciscione AC. Methods of cervical ripening and labor induction: mechanical. Clin Obstet Gynecol 2014; 57(2):369-76.
  14. Di Tommaso M, Seravalli V, Vellucci F, Cozzolino M, Spitaleri M, Susini T. Relationship between cervical dilation and time to delivery in women with preterm labor. J Res Med Sci 2015; 20(10):925-9.
  15. Hofmeyr GJ, Gülmezoglu AM, Pileggi C. Vaginal misoprostol for cervical ripening and induction of labour. Cochrane Database Syst Rev 2010; 10:CD000941.
  16. Ramsey PS, Ogburn PL Jr, Harris DY, Heise RH, DiMarco CS, Ramin KD. Effect of vaginal pH on efficacy of the controlled-release dinoprostone vaginal insert for cervical ripening/labor induction. J Matern Fetal Neonatal Med 2003; 13(4):250-3.
  17. González CA, Salas Guerra A, Arroyo Llano R. Behavior of cervix during pregnancy, labor and puerperium. Ginecol Obstet Mex 2010; 78(2):132-7.
  18. Hawkins JS, Wing DA. Current pharmacotherapy options for labor induction. Expert Opin Pharmacother 2012; 13(14):2005-14.
  19. Dove D, Johnson P. Oral evening primrose oil:Its Effect on Length of Pregnancy and Selected Intrapartum Outcomes in Low-Risk Nulliparous Women. Journal of Midwifery & Women’s Health. 1999;44(3):320-4.
  20. Umeda-Sawada R, Fujiwara Y, Ushiyama I, Sagawa S, Morimitsu Y, Kawashima H, et al. Distribution and metabolism of dihomo-gamma-linolenic acid (DGLA, 20:3n-6) by oral supplementation in rats. Biosci Biotechnol Biochem 2006; 70(9):2121-30.
  21. Blackburn ST. Maternal, fetal & neonatal physiology: a clinical perspective. 4th ed. St. Louis, MO: Saunders Elsevier; 2013
  22. Wettasinghe M, Shahidi F, Amarowicz R. Identification and quantification of low molecular weight phenolic antioxidants in seeds of evening primrose (Oenothera biennis L.). J Agric Food Chem 2002; 50(5):1267-71.
  23. Freitas HR, Isaac AR, Malcher-Lopes R, Diaz BL, Trevenzoli IH, De Melo Reis RA. Polyunsaturated fatty acids and endocannabinoids in health and disease. Nutr Neurosci 2017; 7:1-20.
  24. Nonette DN. The effectiveness of evening primrose oil gel capsule as a cervical ripening agent during labor induction as measured by bishop score on term singleton pregnant patients. Philippine J Obstet Gynecol 2017; 41(2):1-4.
  25. Kalati M, Kashanian M, Jahdi F, Naseri M, Haghani H, Sheikhansari N. Evening primrose oil and labour, is it effective? A randomised clinical trial. J Obstet Gynaecol 2018; 38(4):488-92.
  26. Bayles B, Usatine R. Evening primrose oil. Am Fam Physician 2009; 80(12):1405-8.
  27. Jahdi F, Kalati M, Kashanian M, Naseri M, Haghani H. Effect of oral evening primrose capsules on ripening of the cervix in nulliparous iranian pregnant women (a randomized trial). Acta Med Mediterr 2016; 32:1273-9.
  28. Ty-Torredes KA. The effect of oral evening primrose oil on bishop score and cervical length among term gravidas. Am J Obstet Gynecol 2006; 195(6):S30.
  29. Vahdat M, Tahermanesh K, Kashi AM, Ashouri M, Dodaran MS, Kashanian M, et al. Evening primrose oil effect on the ease of cervical ripening and dilatation before operative hysteroscopy. Thrita 2015; 4(3):e29876.
  30. Hiersch L, Borovich A, Gabbay-Benziv R, Maimon-Cohen M, Aviram A, Yogev Y, et al. Can we predict successful cervical ripening with prostaglandin E2 vaginal inserts? Arch Gynecol Obstet 2017; 295(2):343-9.
  31. Louik C, Gardiner P, Kelley K, Mitchell AA. Use of herbal treatments in pregnancy. Am J Obstet Gynecol 2010; 202(5):439.e1-10.
  32. Wedig KE, Whitsett JA. Down the primrose path: petechial in a neonate exposed to herbal remedy for parturition. J Pediatr 2008; 152(1):140.
  33. Esmaeilzadeh M, Moradi B. Medicinal herbs with side effects during pregnancy-an evidence-based review article. Iran J Obstet Gynecol Infertil 2017; 20:25-9. (Persian).