Research on Dilation

Evidence-based medicine is the way of the future. Check out the extensive research that clinicians and scientists have conducted on cervical dilation and the ways it impacts labor.


Accuracy of Cervical Dilation Examinations

This is the only study of precision of cervical dilation measurements in labor. Two experienced obstetricians measured the same 508 women’s dilations. They agreed on only 49.2% of measurements and disagreed by two or more centimeters for 11% of measurements. 

Buchmann, E and Libhaber E. Accuracy of cervical assessment in the active phase of labour. BJOG. 2007 Jul;114(7):833-7. 

The first study on accuracy of cervical dilation tested 36 midwives and 24 obstetricians using cervical simulators. They chose the correct dilation 48.6% of the time, and no practitioner was correct on all measurements.

Tuffnell, D, Bryce, F, Johnson, N, and Lilford, R. Simulation of Cervical Changes in Labour: Reproducibility of Expert Assessment. Lancet. 1989 Nov 4;2(8671):1089-90.

This trial tested 102 obstetricians and Labor and Delivery nurses using cervical simulators. Overall accuracy was 56.3%. When the same clinician measured the same dilation twice, they disagreed with their own prior measurement 52.1% of the time.

Phelps, J, Higby, K, Smyth, M, Ward, J, Arredondo, F, and Mayer, A. Accuracy and Intraobserver variability of simulated cervical dilatation measurements. Am J Obstet Gynecol. 1995 Sep;173(3 Pt 1):942-5.

Thirty OBGYNs and nurses completed examinations on hard and soft cervical simulators. Accuracy was 54% using the hard models and 19% using soft models, which the authors argue are more realistic.

Huhn, K and Brost, B. Accuracy of simulated cervical dilation and effacement measurements among practitioners. Am J Obstet Gynecol. 2004 Nov;191(5):1797-9.

Need for a Measurement Device

“Although many instruments have been developed to measure cervical dilatation during labor and their use as a research tool has been established, no device has yet been successfully used for clinical obstetrics. The ideal device has not yet been developed; however, because repeated digital cervical examinations are time consuming for the clinician, are poorly reproducible, and are uncomfortable for the patient, continued efforts to develop a cervimeter suitable for clinical use is a worthwhile endeavor.”

Lucidi RS, Blumenfeld LA, Chez RA. Cervimetry: a review of methods for measuring cervical dilation during labor. Obstet Gynecol Surv. 2000 May;55(5):312-20.

“Over the years, many devices have been created to assess labor progress in a more standardized fashion due to the limitations and subjectivity of the digital examination. Additionally, a more objective means of evaluating labor progression is important to further characterize normal versus abnormal labor progress.”

Farine D (ed.). New Technologies for Managing Labor. Berlin/Boston: Walter de Gruyter; 2015. 118 p.

How We Use Dilation

Admission: This study examined the labor course for 216 low-risk, first-time moms. Women admitted before active labor were 39% more likely to receive oxytocin and 9% more likely to have a cesarean delivery.

Neal JL, Lamp JM, Buck JS, Gillespie SL, Ryan SL. Outcomes of Nulliparous Women with Spontaneous Labor Onset Admitted to Hospitals in Pre-active versus Active Labor. J Midwifery Womens Health. 2014 Jan-Feb;59(1):28-34.


Interventions during labor:  This study provides a modern insight on the prevalence of oxytocin (pitocin) use during labor: 80%.

Eggebø TM, Wilhelm-Benartzi C, Hassan WA, et al. A model to predict vaginal delivery in nulliparous women based on maternal characteristics and intrapartum ultrasound. Am J Obstet Gynecol. 2015 Sep; 213;362.e1-6.

Cesarean Section:  13% of cesarean deliveries in the United States are performed because the dilation stopped changing. Cesarean sections for “arrest of dilation” are increasing by 4% per year, significantly contributing to the growing cesarean rate.

Barber EL, Lundsberg LS, Belanger K, Pettker CM, Funai EF, Illuzzi JL. Indications contributing to the increasing cesarean delivery rate. Obstet Gynecol. 2011 Jul;118(1):29-38.