All About Amniotomy (AROM)

I was getting ready for class this weekend, gathering my ‘induction methods’ demo items. And I felt compelled to write a post covering one of the most standard practice medical options, particularly in hospital settings: Amniotomy, also called AROM (Artificial Rupture of Membranes). So let’s learn about it!

Why is AROM Performed?

The intervention is frequently used to induce labor, despite the fact that no evidence exists to demonstrate a causal connection between AROM and success with this goal.

Many people begin experiencing contractions within hours after their water breaks, whether naturally or with medical deliberation. It is hypothesized that the release of amniotic fluid generates hormones that stimulate contractions, though how significant of an impact this has on individual bodies may of course differ. It’s thus debatable whether one who underwent amniotomy progressed into labor on her own, or by cause of the amniotomy. What we know for sure is we cannot force a pregnant person’s body to be ready for labor.

Alas, AROM alone will not likely induce labor, so other induction agents are typically used in tandem or will soon follow. These may include cervical ripeners (synthetic prostaglandins) and/or Pitocin (synthetic oxytocin). A review published on Cochrane Library determined “[e]vidence does not support routinely breaking the waters for women in normally progressing spontaneous labour or where labours have become prolonged.”

Only two well-controlled trials studied the use of amniotomy alone, and the evidence did not support its use for induction of labor.

The American Academy of Family Physicians

In addition to “trying” to start labor, AROM is also used:

  • prior to placement of Internal Fetal Monitor (IFM) / Fetal Scalp Electrode (FSE)
  • for controlled fluid release in cases of polyhydramnios
  • when delivery is imminent, “just because” (though babies can be born in an intact amniotic sac; this is called an ‘en caul’ birth and is not harmful to baby or birth giver)

How is AROM Done?

Amniotomy usually involves inserting an amniohook into the vagina and rupturing the double-layered amniotic membranes with its sharp ‘tooth’ on the end. An amniohook looks similar to a long crochet hook.

The provider holds the amniohook with their non-dominant hand, with dominant-side fingers laying parallel to the device in an attempt to prevent the sharp tooth from injuring vaginal tissues. 

Often this is done during a contraction when when amniotic membranes are more taut. The provider leaves their fingers inside until the water has fully released to ensure the cord hasn’t prolapsed; this can feel physically and/or emotionally uncomfortable for the laborer.

An Amnicot may instead be used; this is a finger covering with a similar hook on the end. It seems like a simpler device, but does carry greater risk of accidental laceration of vaginal and cervical tissues.

What Are The Risks?

An intact (unbroken) bag of water protects baby by keeping contaminants out. It also acts like a ‘water pillow,’ relieving pressure of contractions on baby’s body and the umbilical cord, which is their lifeline. Contractions may feel more manageable as there is a ‘buffer’ of water. 

Many laborers say it is harder to cope with contractions following water breaking, as they increase in intensity. (When water breaks naturally the fluid may release in a gradual manner, rather than emptying all at once, as is the case with AROM).

When an amniotomy is performed, the laborer is typically put on a time clock. This varies between providers but is often 12-24 hours; at which point, they’ll need to either have given birth or be in established active labor (again, depends on the provider). This is due to risk of developing an infection with prolonged rupture of membranes (and, as with most obstetric interventions, due to liability threat).

If this criteria hasn’t been met, the labor may be diagnosed “Failure to Progress” and the laborer will then prepped for cesarean surgery. (“Failure to Wait” may be more appropriate….).

AROM risks include:

  • increased labor pain
  • pain during amniotomy
  • uterine infection
  • infection of baby
  • laceration of baby
  • laceration of cord
  • laceration of cervix / vaginal tissues
  • fetal malposition
  • fetal distress / fetal heart rate deceleration
  • bleeding from low-lying placenta or placenta previa
  • cord compression
  • cord prolapse
  • no effect on length of labor, or labor length is negatively altered
  • unplanned cesarean surgery (“Cascade of Interventions”)

What Are The Benefits?

Potential benefits:

  • hastened cervical dilation, and thus, faster labor (without cushion of water, uterus may be able to squeeze more effectively) — though a shorter labor is not necessarily a safer, easier, or more beneficial one
  • earlier detection of meconium (this isn’t always concerning, however sometimes it can indicate fetal distress and/or cause respiratory problems with heavy meconium)
  • possibility of avoiding pharmacological induction agents for those desiring a drug-free birth, if medical induction is necessary
  • it is inexpensive

How Can You Minimize Risks?

1). Ensure baby’s head is well-applied to the cervix to prevent cord prolapse (cord slipping below baby’s head, which is an obstetric emergency due to compression). Baby should not be in a “floaty” station within the pelvis. P.S. – Know what stations mean!

2). Minimize cervical exams after AROM. This reduces chances of more bacteria entering the vagina and making contact with baby.

3). Regular temperature checks throughout labor to monitor for development of fever.

4). Hire a doula to help you advocate for yourself, to provide you with information, and help you cope with any increased labor pain.

Considerations To Make

That all said, there is a time and a place for just about any intervention. Remember to ask a lot of questions. You can decline ANY procedure, including this one — even if, no especially if, “it’s just how I do things here.”

  • Is this necessary and beneficial for you and baby? In other words, is this being recommend as per routine, or with careful assessment of your situation?
  • What is your Bishop’s Score? (relevant in cases of induction)
  • What is baby’s station (is it a safe time to do AROM)?
  • What happens if you don’t consent?
  • What happens if you do?
  • Are you GBS+? How will that weigh into your decision?
  • Is there an alternative?
  • Is there harm in waiting for your water to break naturally?
  • How do you feel about this? What does your intuition say?

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