Breaking Water to Induce or Augment Labor

Benefits and Risks of an Amniotomy (Artificial Rupture of Membranes)

Pregnant woman timing contractions in hospital
Getty Images/JGI/Jamie Grill

You may have heard that there are many ways to induce labor (or speed it up). One of the methods that people often talk about is breaking the bag waters, a procedure called "amniotomy" or "artificial rupture of membranes" (AROM). In fact, breaking the bag of waters is a labor intervention that has been used by obstetricians and midwives for over a hundred years.

The actual use of amniotomy varies around the world, with the procedure being used routinely in some areas and infrequently in others.

Can breaking the bag of waters help to start or speed up labor, and if so, what role does it play? What are the potential risks of the procedure? And what can you expect if you choose to have your water broken?

Understanding Amniotomy/Breaking the Bag of Water

The amniotic sac lines the uterus and houses the amniotic fluid, baby, and placenta. It provides a barrier to infection for your baby during pregnancy and cushions the baby as you move. It is made up of the amnion and the chorion. So how does breaking water work to induce labor?

An amniotomy may lend itself to labor in both chemical and physical ways. Amniotic fluid contains chemicals and hormones which, when released, are thought to stimulate labor. Physically, the bag of waters can provide a cushion between the baby's head and the cervix.

When the bag of waters is broken (assuming the baby's head is well applied to the cervix) the baby's head can provide more direct pressure on the cervix to help with dilation. When an amniotomy is performed, it is hoped that the procedure will strengthen contractions and speed labor, with the overall goal of shortening labor.

For around 10 percent of women, the bag of waters breaks spontaneously before labor begins. If AROM is not done, the bag usually breaks spontaneously during active labor, anytime between the beginning of labor and delivery of the baby.

Breaking the Bag of Water to Stimulate Labor

Instead of breaking spontaneously, the bag of waters can be broken by a medical professional to either start or augment labor. Let's look at these separately.

  • Induction: An amniotomy may be done before the start of labor to start or induce labor. In some circumstances, an amniotomy may be used alone, although more often it is combined with IV Pitocin. The best methods of starting labor (for whatever indication) depend on the favorability of the cervix (see below). Wih a favorable cervix, the most effective method is usually using a combination of an amniotomy and Pitocin.
  • Augmentation: An amniotomy may also be done after a woman is already in labor, with the hope of speeding up or augmenting labor. (Learn more about the average length of labor). While it does not always speed up the process, it can provide, in some cases, a slight reduction in the need for a cesarean birth (though with some tradeoffs).

Other Benefits of Breaking the Bag of Waters

In addition to induction or augmentation of labor, breaking the bag of water can have some other benefits.

Fetal monitoring: If your baby requires closer monitoring, your obstetrician or midwife may need to break your bag of waters to make this possible. An amniotomy is required in order to perform internal fetal monitoring, as a monitor must be placed on the baby's scalp. Breaking the bag of waters is also needed in order to insert an intrauterine pressure catheter. In this procedure, a catheter is placed in the uterus in order to better determine the strength of your contractions.

Detecting the presence of meconium: Breaking the bag of waters can reveal the presence of meconium-stained amniotic fluid.

If meconium is found with an amniotomy, this gives your health care team time to plan appropriate measures, depending on the thickness of the meconium.

The Procedure

After making sure you are familiar with the procedure and making sure your cervix is "ripe" (see below), your obstetrician or midwife will set you up for the procedure.

Since your bag of waters will be released, your nurse will make sure you have plenty of clean towels underneath you.

Your doctor or midwife will then perform a careful vaginal exam to make sure the baby's head is firmly applied to your cervix. Using an amnihook (a large crochet hook type of device with a small sharp end), or an amnicot (a glove with a small sharp hook at the end of one of the fingers), she will snag your membranes. By creating a tear in the bag, the amniotic fluid will begin to flow out.

The actual breaking of the bag of waters shouldn't be any more painful than a regular vaginal exam to check your cervix. It may unleash a lot of fluid, or instead, it may begin as just a small trickle. Typically you will continue to leak fluid in small amounts for the remainder of your labor.

After your bag is broken, your labor team will monitor your baby and make sure all is well. If you will be getting up to walk, your nurse will give you a large mesh pad to catch the drainage as it continues.

After your water is broken you may notice that you begin to have contractions or you may feel like your baby has dropped further in your pelvis. If you were having contractions before your water was broken, you may feel an increase the intensity of the contractions or you may feel no difference at all.

Before Breaking Your Bag of Waters

Before having an amniotomy either to induce or augment labor, your obstetrician will talk to you about the procedure and discuss the risks and benefits. She will also calculate the likelihood that the procedure will be successful (your Bishop's score) and make sure you don't have any reasons why the procedure should not be done (contraindications).

Determining if Your Cervix is “Favorable”—Bishop’s Score

Before your bag of waters will be broken to induce labor, your obstetrician will calculate a number known as the Bishop's score. The Bishop's score gives an estimate of the "favorability" of your cervix, which in turn can estimate if breaking your bag of waters is likely to start labor or not.

If your cervix is not favorable (if you have a Bishop's score less than 6), induction with amniotomy and Pitocin is usually not recommended and other procedures, such as using prostaglandin gel or Cytotec (misoprostol) to ripen your cervix may be recommended instead. Or you may simply choose to wait until your cervix is more favorable.

Your Bishop's score is calculated by assigning points based on the dilation of your cervix, your effacement (how thin your cervix has become), your fetal station (how low the baby is in your pelvis), and consistency and position. A score of 8 or more means that your cervix is "favorable" and there is a good chance of having a vaginal delivery. Your bag of waters should not be broken unless your fetal station is 0, or positive.

Bishop's Score

Cervical exam0 Points 1 Point2 Points3 Points
Dilation (cm)Closed1-2 cm3-4 cm5-6 cm
Effacement (percent)0-30 percent40-50 percent60-70 percent80 percent
Fetal station-3-2-1, 0+1, +2


Reasons Not To Do An Amniotomy (Contraindications)

There are a few situations in which the bag of waters should not be broken. These are usually fairly obvious and can be determined by reviewing a routine ultrasound (during second trimester or later) and doing a vaginal exam. These include:

  • Abnormal presentation: If the baby is breech or other malpresentation such as face presentation or brow presentation the bag should not be broken.
  • If the baby's head is not engaged or "floating" on an exam. (A fetal station of 0 means the baby's head is fully engaged).
  • Vasa previa: Vasa previa is a rare condition in which the baby's blood vessels from the placenta or umbilical cord pass over the cervix beneath the baby (this can be detected on a routine ultrasound during the second trimester).

Risks and Complications Associated With Breaking the Bag of Water (Amniotomy)

There are relatively few complications associated with an amniotomy, as long as you have a favorable cervix and the baby is engaged. Complications may include:

  • Failure of labor to start: Labor may not begin with breaking the bag of waters and using Pitocin, but at this point, you are usually "committed" to deliver as there is a small risk of infection the longer the bag is broken. (When water breaks on its own before labor begins, the majority of people go into labor within 24 hours).
  • Increase in fetal malposition: If the baby's head is not well applied to the cervix, breaking the bag of water can increase the risk of malposition, and hence, lead to problems with delivery.
  • Cord prolapse (The likelihood of cord prolapse, or the umbilical cord dropping into the vagina in front of the baby, is low if the fetal station is 0).
  • Fetal distress: Uncommonly, breaking the bag of waters can result in fetal distress.
  • Increase in pain (An increase in pain is actually not a complication, but the expected "benefit" if effective, as the start and progression of labor are known to lead to more pain).

There is a slightly increased risk of cesarean delivery when breaking the bag of waters is done for induction (the C-section rate is slightly lower when it is done to augment labor). It's thought that some of these cases are due to detecting the presence of meconium after breaking the bag, and in this sense, an increased C-section rate would not be considered a complication. (With heavy meconium, a C-section may be done to avoid having the baby aspirate the meconium during delivery).

Questions to Ask Before Breaking the Water

Some of the things you will want to know before agreeing to have your water broken include:

  • Will I be allowed to walk after my water is broken?
  • Will I need extra monitoring?
  • What signs of problems will you be looking for and how?
  • How would you guess an amniotomy will change my particular labor?
  • Are there other interventions that may be needed because of this?
  • What are my alternatives?
  • Do I have time to make this decision?

Bottom Line on Breaking Your Bag of Waters to Induce Labor

Obstetricians have used amniotomy or breaking the bag of waters to stimulate labor to begin or progress faster for a century, though we aren't certain the exact role this measure plays. Overall, the risk is small for those who have had a routine ultrasound (to rule out vasa previa), if the baby is well engaged, and if delivery occurs within 24 hours or so. When used for induction of labor, breaking the bag of waters is most often used in combination with pitocin in women who have a favorable cervix.

When looking at the advantages or disadvantages of a labor intervention, it's important to weigh potential risks against potential benefits. We know that pregnancies that extend a week or more beyond the due date can result in complications, and induction is one way to reduce these risks. 

Breaking the bag of waters is also necessary when closer fetal monitoring with an internal fetal monitor and/or intrauterine pressure monitor are recommended.

Every pregnancy is different and it's important that a woman works with her obstetrician to determine what is best for her as an individual. It's important to take into account your entire medical history, the state of your cervix, and your personal preferences.

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