Thursday, February 13, 2014

The Evidence Says: Stripping the membranes not consistently effective but consistently uncomfortable.

Frequently, I am asked to address traditional maternity care procedures and shine the light of evidence on these procedures.  Today, in response to a midwife's request,  The Evidence Says presents the most current findings regarding stripping membranes.

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Induction of labor is a highly controversial topic and one that requires careful consideration. 
Stripping or sweeping of membranes (the amniotic sac near the opening of the cervix) is one method care providers often use. 

How is it done ?

During a vaginal exam, the care provider places a gloved finger into the cervical os.  The closer edge of the membranes is detached from the lower uterine segment in a circular motion – not unlike peeling an orange.

Why is it done?

Stripping the membranes may begin labor by increasing local production of prostaglandins (hormone that will soften the cervix) by stretching of the cervix.  This intervention may shorten pregnancies of women who are at term (41-42 weeks) and may also reduce the need for induction.  However, some studies refute this finding3.

What the evidence indicates:

According to the most prestigious research database, the Cochrane database, stripping of membranes, while possibly shortening pregnancy by initiating cervical softening and irritating the uterine muscle, does not reduce cesarean rates in any population (nulliparous or multiparous women).  There was also no significant difference in maternal or neonatal infections.  It may not be the most effective means of inducing labor when there are medical indications.

Routine use of sweeping of membranes from 38 weeks of pregnancy onwards does not seem to produce clinically important benefits. When used as a means for induction of labor, the reduction in the use of more formal methods of induction needs to be balanced against women's discomfort and other adverse effects.

Discomfort associated with stripping membranes includes irregular contractions, spotting/bleeding, cramping and general discomfort – all of which may last for up to 24 hours.

Reasons You Would Not Want Your Membranes Stripped:

According to the American College of Nurse-Midwives (ACNM) Fact Sheet on Stripping Membranes1, there are five reasons why an expectant mother may not want her membranes stripped.  They include:

  • You have been told that it is not safe to have your infant vaginally.
  • You have had unexplained vaginal bleeding during your pregnancy.
  • You have been told that you need to have your infant urgently and it would be safest to have your labor induced by using medication.
  • You want to let your pregnancy and labor unfold naturally and there is no medical reason to have your labor induced.
  • If you have had a vaginal culture that says you have group B strep (GBS) in your vagina, you may not want to have your membranes stripped; there are no studies that have shown it is safe if you have GBS so this decision should be made with you and your care-provider making the decision together.

When might induction improve health outcomes of mothers and babies:

According to two studies4,5, three situations showed small improvements in outcomes but left many unanswered questions.  These situations included:

  • Pregnancy lasting beyond 41 weeks.
  • Prelabor rupture of membranes at term.
  • Increased blood pressure/preeclampsia at the end of pregnancy.

And a final word on reasons for induction that are not supported by research:

  • Preterm prelabor rupture of membranes.
  • Twin pregnancy.
  • Gestational Diabetes requiring insulin.
  • Intrauterine growth restriction (IUGR) before 37 weeks or at term.
  • Oligohydramnios (too little amniotic fluid).
  • Concern that the baby will get to big (suspected macrosomia).

Stripping of membranes and other mechanical methods of labor induction may begin labor but may also lead to additional interventions and methods of induction (such as Pitocin/ Syntocin) or even Cytotec.  It is important for careproviders to share all information with expectant mothers so that a well-thought out decision can be made.

References and Resources:

  1. ACNM (2009) Fact Sheet: Stripping Membranes. Journal of Midwifery and Womens Health.
  2. Boulvain, M. et al (2005) Cochrane Database: Membrane sweeping for induction. Last accessed 2/13/14;jsessionid=D4F9ECF1A89EEAB8143B5930D810A792.f03t02
  3. Kashanian, M. et al. (2006) Effect of membrane sweeping at term pregnancy on duration of pregnancy and labor induction: a randomized trial. Gynecologic and Obstetric Investigation. 62(1): 41-4.
  4. Koopmans CM, Bijlenga D, Groen H, et al. Induction of labour versus expectant monitoring for gestational hypertension or mild pre-eclampsia after 36 weeks' gestation (HYPITAT): A multicentre, open-label randomised controlled trial. Lancet. 2009;374(9694):979-988. 
  5. Mozurkewich E, Chilimigras J, Koepke E, Keeton K, King VJ. Indications for induction of labour: A best-evidence review. British Journal of Obstetrics & Gynecology. 2009;116(5):626-636.

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