Amniotomy and Cord Prolapse
by Judy Slome Cohain
© 2013 Midwifery Today, Inc. All rights reserved.
[Editor’s note: This is an excerpt of an article which appears in Midwifery Today, Issue 108, Winter 2013. View other great articles and columns in the table of contents. To read the rest of this article, order your copy of Midwifery Today, Issue 108.]
Abstract: Research shows that artificially rupturing the amniotic sac (amniotomy) can cause umbilical cord prolapse. Amniotomy became a routine part of obstetrical care with the introduction of active management, without evidence of benefit. In the 30 years since active management was introduced, the rate at which amniotomy causes umbilical cord prolapse has not been directly studied. Two controlled studies from Turkey from 2002 and 2006 are the only published studies that provide enough data to extract the rate at which cord prolapse follows amniotomy. They show that 1 cord prolapse results from every 300 amniotomies (0.3%). There is data suggesting amniotomy may also increase neonatal GBS infection, maternal pain and fetal blood loss if placental blood vessels are punctured.
Rate of cord prolapse directly increases with increasing rates of amniotomy. Where amniotomy is never practiced and vaginal exams are extremely restricted, no cord prolapse is reported. Rates of 3–4/1000 cord prolapses were reported with 26–89% rates of amniotomy (Dilbaz 2006; Uygur 2002). In a study of inductions, which usually include amniotomy, a 7/1000 rate of cord prolapse was reported.
The incidence of cord prolapse has been said to range from 0.1% to 0.6% (Lin 2006). About 10% of full-term births, excluding inductions, start with spontaneous rupture of membranes (Dilbaz et al. 2006; Zlatnik 1992). Amniotomy is routinely performed at most hospital births during the first stage of labor when the sac does not break spontaneously at the beginning of labor. Practitioners practicing in environments where vaginal exams are routine generally think that membranes rupture spontaneously during the first stage of labor. This may be because the sac often ruptures directly following, and likely as a result of, a vaginal exam. Practitioners who practice no routine vaginal exams and 0.4% rates of amniotomy report either the sac breaks at the start of labor, the sac does not break until the woman pushes (86%) or the fetal head emerges in an intact sac (4%) (Cohain 2010).
In 1984, Dublin’s active management was introduced including amniotomy as a part of the protocol to prevent cesareans for dystocia (O’Driscoll, Foley and MacDonald 1984). Parts of this protocol, such as amniotomy, were widely adopted in the absence of strong evidence that selective parts of the protocol were independently advantageous.
- Cohain, JS. 2010. “Newborn Group B Strep Infection: Top 10 Reasons Not to Culture for GBS at 36 Weeks.” Midwifery Today Int Midwife 94:15.
- Dilbaz, B, et al. 2006. “Risk Factors and Perinatal Outcomes Associated with Umbilical Cord Prolapse.” Arch Gynecol Obstet 274 (2): 104–07.
- Lin, MG. 2006. “Umbilical Cord Prolapse.” Obstet Gynecol Surv 61 (4): 269–77.
- O’Driscoll, K, M Foley and D MacDonald. 1984. “Active Management of Labor as an Alternative to Cesarean Section for Dystocia.” Obstet Gynecol 63 (4): 485–90.
- Uygur, D, et al. 2002. “Risk Factors and Infant Outcomes Associated with Umbilical Cord Prolapse.” Int J Gynaecol Obstet 78:127–30.
- Zlatnik, FJ. 1992. “Management of Premature Rupture of Membranes at Term.” Obstet Gynecol Clin North Am 19:353–64.
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