by Eva Martin, MD

When I speak to women in their first pregnancies, they usually have no idea what cervical dilation is. But, ask any mom who has gone through labor, and she can tell you it’s very important.

The cervix is the doorway from the womb (uterus) to the birth canal. When a woman is not pregnant, her cervix is firm, long, and closed. During pregnancy, the cervix should stay closed so that the baby can safely grow inside the uterus. When the time finally comes for the baby’s birthday, labor starts.

In the medical literature, the very definition of labor is “contractions that bring about cervical change.”

There are several stages of labor. The first stage is the slow opening up, or dilation, of the cervix. The strength of the body’s contractions enable this doorway to slowly open to allow the baby to move from the womb into the birth canal. The cervix is completely dilated when it is ten centimeters wide. When the cervix is completely dilated, the healthcare provider can no longer feel any cervix around the baby’s head. Any seasoned mom will tell you- the labor process is difficult, and each centimeter along the way to complete dilation is crucial.

During the first stage of labor, providers check cervical dilation to track how labor is progressing. For decades, obstetrician-researchers have tried to model how safe labor looks so that they can intervene if the labor pattern is unsafe for the mother or baby.[1] Generally speaking, the first few centimeters from zero to four centimeters dilation are slower, and the cervix opens more quickly at the end. For this reason, most providers try to only admit laboring women to the hospital when the dilation is at least four to six centimeters, or during the faster part of labor.

The dilation does not only help healthcare providers judge whether a woman is in labor and whether it is time to admit her to the hospital, but it also guides decisions throughout the labor course. If the dilation stops changing, a healthcare provider will often recommend interventions to encourage it to dilate more. The most common of these are intentionally breaking the bag of water or giving a drug called oxytocin or pitocin. Oxytocin strengthens contractions, but it is not without risks. Up to 80% of women in labor currently receive oxytocin.[2] If the dilation does not change for several hours despite adequate contractions, providers will recommend a cesarean birth. 18% of all cesarean births in the United States are performed because labor has stopped progressing.[3]

What exactly is happening when providers “check the dilation?”

Currently, we check dilation by feeling for the cervix with two fingers. Since the cervix is at the back of the birth canal, we must use feel and not sight. We place two fingers at opposite sides of the cervical opening and estimate how far apart our fingers feel. As you might imagine, this technique is inaccurate. In trials using simulators, doctors, midwives, and nurses get the correct measurement only about 50% of the time.[4],[5],[6] If two expert obstetricians check the same cervix, they only agree on the dilation 49% of the time.[7] This can create uncertainty and confusion, but there are currently no tools in general use to solve this problem.

Cervical dilation is the key metric for diagnosing labor. It tells providers whether it is time to admit a woman to the hospital and whether they should recommend interventions, medications, or even a cesarean birth. The number is inaccurate, often leading to confusion. My life’s work is to create a more accurate way to measure this important number, so I invented a measuring tool called DilaCheck® .

If you have a question about this topic or would like to share your story about how cervical dilation played a role in your labor experience, please email me at evamartin@elmtreemedical.com. I always welcome speaking with new and expecting moms and families, and healthcare practitioners!

This article is for educational purposes only and is not medical advice. Each case is individual, so please consult with your medical care provider.

BIOGRAPHY

Eva is the founder and CEO of Elm Tree Medical Inc., a medical device company focused on women’s health. She graduated cum laude from Harvard College, conducted breast cancer research at the University of California, San Francisco, and earned her MD from Harvard Medical School. Following medical school, Eva completed her internship training in OBGYN at Kaiser Permanente San Francisco, where she delivered hundreds of beautiful babies. In June 2015, she founded Elm Tree Medical Inc. and currently works full time as Elm Tree Medical’s CEO. Elm Tree Medical is developed a tool (DilaCheck®) to increase accuracy in cervical dilation measurements.

To learn more, please visit our website, follow us on Twitter, or connect with us on Facebook.

_________________________________________________________________

[1]Zhang J et al. Contemporary Patterns of Spontaneous Labor with Normal Neonatal Outcomes. Obstet & Gynecol. 2010 Dec; 115(6):1281-1287.[2]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.[3]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.[4]Tuffnel, et al. Simulation of cervical changes in labour: reproducibility of expert assessment. The Lancet. 1989. Nov;1089-1090.[5]Phelps J, Higby K, Smyth M, Ward J, Arredondo F, Mayer A. Accuracy and Intraobserver variability of simulated cervical dilatation measurements. Am J Obstet Gynecol. 1995 Sep;173(3 Pt 1):942-5.[6]Huhn K, Brost B. Accuracy of simulated cervical dilation and effacement measurements among practitioners. Am J Obstet Gynecol. 2004 Nov;191(5):1797-9. [7]Buchmann E, Libhaber E. Accuracy of cervical assessment in the active phase of labour. BJOG. 2007 Jul;114(7):833-7.