A novel method for assessing the condition of the cervix before labor induction: Cervical length/thickness ratio

Ultrasonographic observation of cervical ripening



Cervix uteri, Cervical length, Ultrasonography, Cervical thickness


Background/Aim: Due to the increasing cesarean rates globally, new methods for supporting vaginal delivery and induction of successful vaginal delivery are still being developed. We aimed to obtain an easy-to-use method that can predict the effectiveness of cervical ripening agents before labor induction. So, we presented the effects on labor by measuring the thickness of the cervix and the cervical length/thickness ratio ultrasonographically.

Methods: In this prospective cohort study, we evaluated 183 pregnant between 37 and 41 weeks of gestational age and will apply vaginal delivery induction. Before oxytocin induction, we applied 10 mg dinoprostone vaginally to women whose cervix was stiff. We started labor induction with oxytocin when regular uterine contractions or dilatation occurred. We used the Bishop Scoring System for favorable cervix defining. Then, we compared the groups with successful and unsuccessful cervical ripening regarding cervical length and thickness parameters.

Results: The mean cervical thickness of the pregnant women with successful cervical ripening was 34.5 (7.5) mm before treatment, while the mean values of the unsuccessful group were 29.2 (9.1) mm (P < 0.001). The cervical length did not differ between the two groups (31.6 [8.2] vs. 32.5 [6.8], P = 0.44), while the cervical length/thickness ratio was lower in the group with successful ripening (0.9 [0.38–2], P < 0.001). Cervical length/thickness ratio was the highest predictor of the favorable cervix with dinoprostone. Each 1 unit decrease in the length/thickness ratio of the cervix increases the preparation of the cervix for induction by 0.25 times (P = 0.04). A successful response to dinoprostone can be obtained if the cervical length/thickness ratio is <1.06 mm (P < 0.001).

Conclusion: In conclusion, assessing the cervix’s condition before labor induction by measuring the cervical length/thickness ratio may be a good predictor of cervical ripening activity.


Download data is not yet available.


Carlson LC, Feltovich H, Palmeri ML, Rio AM del, Hall TJ. Statistical analysis of shear wave speed in the uterine cervix. IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control. 2014;61(10):1651–60. DOI: https://doi.org/10.1109/TUFFC.2014.006360

Read CP, Word RA, Ruscheinsky MA, Timmons BC, Mahendroo MS. Cervical remodeling during pregnancy and parturition: molecular characterization of the softening phase in mice. Reproduction. 2007;134(2):327–40. DOI: https://doi.org/10.1530/REP-07-0032

Tajik P, van der Tuuk K, Koopmans CM, Groen H, van Pampus MG, Van Der Berg PP, et al. Should cervical favourability play a role in the decision for labour induction in gestational hypertension or mild pre‐eclampsia at term? An exploratory analysis of the HYPITAT trial. BJOG. 2012;119(9):1123–30. doi: 10.1111/j.1471-0528.2012.03405.x. DOI: https://doi.org/10.1111/j.1471-0528.2012.03405.x

Bernardes TP, Broekhuijsen K, Koopmans CM, Boers KE, Van Wyk L, Tajik P, et al. Caesarean section rates and adverse neonatal outcomes after induction of labour versus expectant management in women with an unripe cervix: a secondary analysis of the HYPITAT and DIGITAT trials. BJOG. 2016;123(9):1501–8. doi: 10.1111/1471-0528.14028. DOI: https://doi.org/10.1111/1471-0528.14028

American College of Obstetricians and Gynecologists. ACOG practice bulletin no. 107: induction of labor. Obstet Gynecol. 2009;114:386–97. DOI: https://doi.org/10.1097/AOG.0b013e3181b48ef5

Vaknin Z, Kurzweil Y, Sherman D. Foley catheter balloon vs locally applied prostaglandins for cervical ripening and labor induction: a systematic review and meta-analysis. Am J Obstet Gynecol. 2010;203(5):418–29. DOI: https://doi.org/10.1016/j.ajog.2010.04.038

Chen W, Xue J, Peprah MK, Wen SW, Walker M, Gao Y, et al. A systematic review and network meta-analysis comparing the use of Foley catheters, misoprostol, and dinoprostone for cervical ripening in the induction of labour. BJOG: an International J Obstet Gynaecol. 2016;123(3):346–54. DOI: https://doi.org/10.1111/1471-0528.13456

Fox NS, Saltzman DH, Roman AS, Klauser CK, Moshier E, Rebarber A. Intravaginal misoprostol versus Foley catheter for labour induction: a meta-analysis. BJOG: an International J Obstet Gynaecol. 2011;118(6):647–54. DOI: https://doi.org/10.1111/j.1471-0528.2011.02905.x

Grobman W. Induction of labor: Techniques for preinduction cervical ripening. 2022. Available from: https://www.uptodate.com/contents/induction-of-labor-techniques-for-preinduction-cervical-ripening

Yount SM, Lassiter N. The pharmacology of prostaglandins for induction of labor. Journal of Midwifery & Women’s Health. 2013;58(2):133–9. DOI: https://doi.org/10.1111/jmwh.12022

Zeng X, Zhang Y, Tian Q, Xue Y, Sun R, Zheng W, et al. Efficiency of dinoprostone insert for cervical ripening and induction of labor in women of full-term pregnancy compared with dinoprostone gel: a meta-analysis. Drug Discoveries & Therapeutics. 2015;9(3):165–72. DOI: https://doi.org/10.5582/ddt.2015.01033

Nisiya KS, Devi U, Ahmed FM. A prospective study on comparison of effectiveness and safety of dinoprostone intracervical gel and dinoprostone vaginal insert on induction of labour. Int J Clin Obstet Gynaecol 2022;6(1):152-60. doi: 10.33545/gynae.2022.v6.i1c.1130 DOI: https://doi.org/10.33545/gynae.2022.v6.i1c.1130

Ragusa A, De Luca C, Zucchelli E, Svelato A. What will be the future of dinoprostone in labor induction? Int J Gynaecol Obstet. 2022 Jun;157(3):751-2. doi: 10.1002/ijgo.14086. DOI: https://doi.org/10.1002/ijgo.14086

Chaiworapongsa T, Espinoza J, Kalache K, Gervasi MT, Romero R. Sonographic examination of the uterine cervix. The Fetus as a Patient: the Evolving Challenge New York: Parthenon. 2002;90–117.

Aboulghar M, Rizk B. Ultrasonography of the cervix. In: Rizk BRMB, editor. Ultrasonography in Reproductive Medicine and Infertility. Cambridge: Cambridge University Press; 2010. p. 103–12. Available from: https://www.cambridge.org/core/books/ultrasonography-in-reproductive-medicine-and-infertility/ultrasonography-of-the-cervix/A36631D429EAD8DB29AC2FDF0E28EC85 DOI: https://doi.org/10.1017/CBO9780511776854.015

Chao A-S, Chao A, Hsieh PC-C. Ultrasound assessment of cervical length in pregnancy. Taiwan J Obstet Gynecol. 2008 Sep;47(3):291-5. doi: 10.1016/S1028-4559(08)60126-6. PMID: 18935991. DOI: https://doi.org/10.1016/S1028-4559(08)60126-6

Burger M. Weber-R össler T, Willmann M. Measurement of the pregnant cervix by transvaginal sonography: an interobserver study and new standards to improve the interobserver variability. Ultrasound Obstet Gynecol. 1997;9:188–93. DOI: https://doi.org/10.1046/j.1469-0705.1997.09030188.x

Gomez R, Galasso M, Romero R, Mazor M, Sorokin Y, Gonçalves L, et al. Ultrasonographic examination of the uterine cervix is better than cervical digital examination as a predictor of the likelihood of premature delivery in patients with preterm labor and intact membranes. Am J Obstet Gynecol. 1994 Oct;171(4):956-64. doi: 10.1016/0002-9378(94)90014-0. DOI: https://doi.org/10.1016/0002-9378(94)90014-0

Louwagie EM, Carlson L, Over V, Mao L, Fang S, Westervelt A, et al. Longitudinal ultrasonic dimensions and parametric solid models of the gravid uterus and cervix. PLOS ONE. 2021;16(1):e0242118. doi: 10.1371/journal.pone.0242118. DOI: https://doi.org/10.1371/journal.pone.0242118

Zhang J, Troendle J, Mikolajczyk R, Sundaram R, Beaver J, Fraser W. The natural history of the normal first stage of labor. Obstet Gynecol. 2010 Apr;115(4):705-10. doi: 10.1097/AOG.0b013e3181d55925. Erratum in: Obstet Gynecol. 2010 Jul;116(1):196. DOI: https://doi.org/10.1097/AOG.0b013e3181d55925

Ehsanipoor RM, Satin AJ. Labor: Overview of normal and abnormal progression. 2022. Available from: https://www.uptodate.com/contents/labor-overview-of-normal-and-abnormal-progression

Bishop EH. Pelvic scoring for elective induction. Obstet Gynecol. 1964;24:266-8.

Krammer J, Williams MC, Sawai SK, O’Brien WF. Pre-induction cervical ripening: a randomized comparison of two methods. Obstet Gynecol. 1995;85(4):614–8. DOI: https://doi.org/10.1016/0029-7844(95)00013-H

Porto M. The unfavorable cervix: methods of cervical priming. Clin Obstet Gynecol. 1989;32(2):262–8. DOI: https://doi.org/10.1097/00003081-198906000-00009

Boulvain M, Kelly A, Lohse C, Stan C, Irion O. Mechanical methods for induction of labour. The Cochrane Database of Systematic Reviews. 2001;(4):CD001233. DOI: https://doi.org/10.1002/14651858.CD001233

de Vaan MDT, Ten Eikelder ML, Jozwiak M, Palmer KR, Davies‐Tuck M, Bloemenkamp KWM, et al. Mechanical methods for induction of labour. Cochrane Database Syst Rev. 2019 Oct 18;10(10):CD001233. doi: 10.1002/14651858.CD001233.pub3. DOI: https://doi.org/10.1002/14651858.CD001233.pub3

Kelly AJ, Malik S, Smith L, Kavanagh J, Thomas J. Vaginal prostaglandin (PGE2 and PGF2a) for induction of labour at term. Cochrane Database Syst Rev. 2009 Oct 7;(4):CD003101. doi: 10.1002/14651858.CD003101.pub2. Update in: Cochrane Database Syst Rev. 2014;6:CD003101. PMID: 19821301. DOI: https://doi.org/10.1002/14651858.CD003101.pub2

Verhoeven CJM, Opmeer BC, Oei SG, Latour V, van der Post JAM, Mol BWJ. Transvaginal sonographic assessment of cervical length and wedging for predicting outcome of labor induction at term: a systematic review and meta-analysis. Ultrasound Obstet Gynecol. 2013;42(5):500–8. DOI: https://doi.org/10.1002/uog.12467

Crane JMG. Factors predicting labor induction success: a critical analysis. Clin Obstet Gynecol. 2006;49(3):573–84. DOI: https://doi.org/10.1097/00003081-200609000-00017

Lauterbach R, Ben Zvi D, Dabaja H, Zidan R, Justman N, Vitner D, et al. Vaginal dinoprostone insert versus cervical ripening balloon for term induction of labor in obese nulliparas—a randomized controlled trial. J Clin Med. 2022 Apr 11;11(8):2138. doi: 10.3390/jcm11082138. DOI: https://doi.org/10.3390/jcm11082138

Bagory H, De Broucker C, Tourneux P, Balcaen T, Gondry J, Foulon A, et al Efficacité et tolérance du misoprostol oral 25μg vs dinoprostone vaginale dans le déclenchement du travail à terme [Efficacy and safety of oral misoprostol 25μg vs. vaginal dinoprostone in induction of labor at term]. Gynecol Obstet Fertil Senol. 2022 Mar;50(3):229-35. French. doi: 10.1016/j.gofs.2021.11.011. DOI: https://doi.org/10.1016/j.gofs.2021.11.011

Garg R, Bagga R, Kumari A, Kalra J, Jain V, Saha SC, et al. Comparison of intracervical Foley catheter combined with a single dose of vaginal misoprostol tablet or intracervical dinoprostone gel for cervical ripening: a randomised study. J Obstet Gynaecol. 2022;42(2):232–8. doi: 10.1080/01443615.2021.1904227. DOI: https://doi.org/10.1080/01443615.2021.1904227

Heath VCF, Southall TR, Souka AP, Elisseou A, Nicolaides KH. Cervical length at 23 weeks of gestation: prediction of spontaneous preterm delivery. Ultrasound Obstet Gynecol. 1998;12(5):312–7. doi: 10.1046/j.1469-0705.1998.12050312.x. DOI: https://doi.org/10.1046/j.1469-0705.1998.12050312.x

Andersen HF, Nugent CE, Wanty SD, Hayashi RH. Prediction of risk for preterm delivery by ultrasonographic measurement of cervical length. Am J Obstet Gynecol. 1990 Sep;163(3):859-67. doi: 10.1016/0002-9378(90)91084-p. DOI: https://doi.org/10.1016/0002-9378(90)91084-P

Berghella V, Roman A, Daskalakis C, Ness A, Baxter JK. Gestational age at cervical length measurement and incidence of preterm birth. Obstet Gynecol. 2007 Aug;110(2 Pt 1):311-7. doi: 10.1097/01.AOG.0000270112.05025.1d. DOI: https://doi.org/10.1097/01.AOG.0000270112.05025.1d

Hassan SS, Romero R, Berry SM, Dang K, Blackwell SC, Treadwell MC, et al. Patients with an ultrasonographic cervical length ≤15 mm have nearly a 50% risk of early spontaneous preterm delivery. Am J Obstet Gynecol. 2000;182(6):1458–67. DOI: https://doi.org/10.1067/mob.2000.106851

Grimes-Dennis J, Berghella V. Cervical length and prediction of preterm delivery. Curr Opin Obstet Gynecol. 2007 Apr;19(2):191-5. doi: 10.1097/GCO.0b013e3280895dd3. DOI: https://doi.org/10.1097/GCO.0b013e3280895dd3

Rane SM, Guirgis RR, Higgins B, Nicolaides KH. Pre-induction sonographic measurement of cervical length in prolonged pregnancy: the effect of parity in the prediction of the need for Cesarean section. Ultrasound Obstet Gynecol. 2003;22(1):45–8. doi: 10.1002/uog.166 DOI: https://doi.org/10.1002/uog.166

Rane SM, Pandis GK, Guirgis RR, Higgins B, Nicolaides KH. Pre-induction sonographic measurement of cervical length in prolonged pregnancy: the effect of parity in the prediction of induction-to-delivery interval. Ultrasound Obstet Gynecol. 2003;22(1):40–4. doi: 10.1002/uog.165. DOI: https://doi.org/10.1002/uog.165

Pandis GK, Papageorghiou AT, Ramanathan VG, Thompson MO, Nicolaides KH. Preinduction sonographic measurement of cervical length in the prediction of successful induction of labor. Ultrasound Obstet Gynecol. 2001;18(6):623–8. doi: 10.1046/j.0960-7692.2001.00580.x. DOI: https://doi.org/10.1046/j.0960-7692.2001.00580.x

Park KH, Kim SN, Lee SY, Jeong EH, Jung HJ, Oh KJ. Comparison between sonographic cervical length and Bishop score in preinduction cervical assessment: a randomized trial. Ultrasound Obstet Gynecol. 2011;38(2):198–204. doi: 10.1002/uog.9020. DOI: https://doi.org/10.1002/uog.9020

Laencina Anamg, Sánchez FG, Gimenez JH, Martínez MS, Martínez JAV, Vizcaíno VM. Comparison of ultrasonographic cervical length and the Bishop score in predicting successful labor induction. Acta Obstet Gynecol Scand. 2007;86(7):799-804. doi: 10.1080/00016340701409858. DOI: https://doi.org/10.1080/00016340701409858

Cubal A, Carvalho J, Ferreira MJ, Rodrigues G, Carmo O Do. Value of Bishop score and ultrasound cervical length measurement in the prediction of cesarean delivery. J Obstet Gynaecol Research. 2013;39(9):1391–6. doi: 10.1111/jog.12077. DOI: https://doi.org/10.1111/jog.12077

Dilek TUK, Gurbuz A, Yazici G, Arslan M, Gulhan S, Pata O, et al. Comparison of cervical volume and cervical length to predict preterm delivery by transvaginal ultrasound. Am J Perinatol. 2006 Apr;23(3):167-72. doi: 10.1055/s-2006-934102. DOI: https://doi.org/10.1055/s-2006-934102

Valentin L, Bergelin I. Intra- and interobserver reproducibility of ultrasound measurements of cervical length and width in the second and third trimesters of pregnancy. Ultrasound Obstet Gynecol. 2002;20(3):256-62. doi: 10.1046/j.1469-0705.2002.00765.x. DOI: https://doi.org/10.1046/j.1469-0705.2002.00765.x






Research Article

How to Cite

Karaşin SS. A novel method for assessing the condition of the cervix before labor induction: Cervical length/thickness ratio: Ultrasonographic observation of cervical ripening. J Surg Med [Internet]. 2022 Aug. 31 [cited 2022 Sep. 28];6(8):729-34. Available from: https://jsurgmed.com/article/view/7357