AROM (Artificial Rupture of Membranes): Why is it Done, and What Does it Really Do?

An OB or midwife may recommend to their patient that they should perform an amniotomy (break the bag of waters) for any these reasons:

• in a stalled or prolonged (spontaneous) labor to "speed things up"

• to induce labor (either alone, or in conjunction with labor-inducing drugs) 

• to place an internal fetal monitor

• to check for meconium in the amniotic fluid in the case of fetal distress

Are these reasons evidence-based? Some are, yes. Others are not.

• As far as breaking the water to speed up labor goes, this is not based in any scientific fact. The evidence is actually against it. AROM has been debunked as a method of speeding up labor, with most studies saying that it does not significantly speed up labor, and if it does, it only shortens labor by maybe an hour, at most. The Cochrane Review on this subject states that "Evidence does not support routinely breaking the waters for women in normally progressing spontaneous labor or where labors have become prolonged."

• When it comes to breaking the water as the sole means to induce labor, ACOG states that "Used alone for inducing labor, amniotomy can be associated with unpredictable and sometimes long intervals before the onset of contractions. There is insufficient evidence on the efficacy and safety of amniotomy alone for labor induction." Essentially, it's not reliable, may not be safe, and doesn't do what we've been told it's supposed to do (which is jump-start contractions and get labor going).

• If there is legitimate concern about fetal well-being, such as irregular heartbeat and signs of distress, it may become necessary to break the waters (if they have not broken already) in order to place an internal fetal monitor. In this case, the benefits (keeping a closer eye on baby and maybe saving baby's life) may outweigh the risks.

• This is the same as above. If there are real signs of distress, breaking the water to check for meconium can help you and your doctor to make the best decision, with all the facts in hand, about how to continue in your labor. If baby is truly distressed, has passed meconium, and there are other problems as well, you might need to have an emergency cesarean. This is not to say that it is impossible to vaginally have a healthy baby who has passed meconium in the womb (because it absolutely is, and about 20% of babies after 40 weeks gestation will pass meconium as their bowels reach maturity and begin to work), but it can be a red flag for complications. 

So what are the risks of amniotomy/AROM/breaking the water? Why would you not want it performed?

• It may increase the strength and intensity (and pain level) of contractions, because it essentially removes the cushion of fluid from around the baby, and causes baby's head to come into more direct contact with mom's cervix (ouch!). This can lead to mom asking for pain medications, such as an epidural, which leads to less physiological labor and pushing positions, which leads to other interventions...well, you see where this is going. The old "cascade/slippery slope."
• The baby may go into distress due to compression of the cord, the placenta, or the baby him/her self.
• Studies have found that amniotomy can alter fetal vascular blood flow, which suggests that there may be a fetal distress response to AROM.
• AROM may cause what is called "cord prolapse," which happens when baby's head is not engaged when the waters are broken, and the cord is swept out of the cervix by the fluid and baby's head then comes down, compressing the cord and cutting off baby's blood/oxygen supply. This is a severe emergency situation, and the baby must immediately be born by cesarean. This is a life-or-death complication that can be directly caused by medical intervention (AROM).
• There may be a blood vessel running through the membranes, and if that vessel is is ruptured by the amni-hook during AROM, the baby could lose a lot of blood, fast. This is another emergency situation that requires a cesarean, caused directly by an intervention.
• There is a (very slight) increase in the risk of infection after AROM, but this is more of a risk to mom than baby, and the risk is greatly reduced if nothing is introduced into the vagina during labor (as with cervical checks, etc.).
• Early amniotomy, on its own, increases your risk of having a cesarean delivery.

To sum up, AROM increases your risk of fetal distress, infection, cord prolapse, cesarean section, maternal and fetal blood loss, and opens the door for further interventions, which themselves carry risks. AROM does not, as some will tell you, significantly speed up a stalled labor, and it is not effective/reliable as a method of labor induction, either. So unless there is a life-threatening or possible emergent situation, it is best to leave the waters intact and not artificially break them. There are too many risks, and not enough evidence of any benefits, to justify AROM without a medical necessity.

1. Evidence does not support routinely breaking the waters for women in normally progressing spontaneous labour or where labours have become prolonged. - See more at: http://summaries.cochrane.org/CD006167/amniotomy-for-shortening-spontaneous-labour#sthash.tyjUw2Pr.dpuf
   Evidence does not support routinely breaking the waters for women in normally progressing spontaneous labour or where labours have become prolonged. - See more at: http://summaries.cochrane.org/CD006167/amniotomy-for-shortening-spontaneous-labour#sthash.tyjUw2Pr.dpuf
   Evidence does not support routinely breaking the waters for women in normally progressing spontaneous labour or where labours have become prolonged. - See more at: http://summaries.cochrane.org/CD006167/amniotomy-for-shortening-spontaneous-labour#sthash.tyjUw2Pr.dpuf
   Evidence does not support routinely breaking the waters for women in normally progressing spontaneous labour or where labours have become prolonged. - See more at: http://summaries.cochrane.org/CD006167/amniotomy-for-shortening-spontaneous-labour#sthash.tyjUw2Pr.dpuf
   Evidence does not support routinely breaking the waters for women in normally progressing spontaneous labour or where labours have become prolonged. - See more at: http://summaries.cochrane.org/CD006167/amniotomy-for-shortening-spontaneous-labour#sthash.tyjUw2Pr.dpu