Breaking Water to Induce or Augment Labor

The benefits and risks of amniotomy.

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

There are many ways to induce or speed up labor. One method people often talk about is intentionally breaking the bag of water (amniotic sac) around the baby. This procedure is called "amniotomy" or "artificial rupture of membranes" (AROM).

Purposefully breaking the amniotic sac as a labor intervention has been used by obstetricians and midwives for more than one hundred years. Today, the use of amniotomy varies around the world. The procedure is used routinely in some parts of the world and infrequently in others.

Understanding Amniotomy/Breaking the Bag of Water

The amniotic sac is made up of two membranous layers: the amnion and the chorion. The sac lines the uterus and houses the amniotic fluid, the placenta, and is where the fetus develops during pregnancy. In addition to providing a barrier to infection, the sac also cushions the fetus as the mother moves about.

Around 10 percent of women experience a spontaneous rupture of membranes. When her "water breaks," it is usually considered a sign labor is beginning.

In some cases, the sac may not open up on its own as labor begins. A woman's doctor or midwife may recommend the sac be ruptured intentionally in a procedure called amniotomy.

An amniotomy is performed in hopes of strengthening contractions and speeding up labor, with the overall goal of shortening labor. The procedure may influence labor in both chemical and physical ways. Amniotic fluid contains chemicals and hormones which, when released, are thought to stimulate labor.

Physically, the sac provides a cushion between the baby's head and the cervix. If the baby's head is well applied to the cervix, breaking the bag of waters allows the head to apply more direct pressure on the cervix to encourage dilation.

If amniotomy is not performed, the sac will usually spontaneously rupture during active labor; anytime between the first signs of labor and delivery.

Breaking the Bag of Water to Stimulate Labor

If the amniotic sac does not rupture spontaneously, the bag of waters can be broken by a medical professional to either start or augment labor.

  • Induction: Amniotomy may be done to start or induce labor. In some cases, amniotomy may be used alone. More often the procedure is combined with IV Pitocin. The best method for starting labor (for any indication) depends on the favorability of the cervix. With a favorable cervix, the most effective method is usually a combination of amniotomy and Pitocin.
  • Augmentation: 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, in some cases it can provide 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 inducing or augmenting labor, there are other potential benefits to artificial rupture of membranes (AROM):

Fetal monitoring: If your baby requires close monitoring, your obstetrician or midwife may need to break the amniotic sac. Amniotomy is required when internal fetal monitoring is needed, as a monitor must be placed on the baby's scalp. Breaking the bag of waters must also be done to insert an intrauterine pressure catheter. In this procedure, a catheter is placed in the uterus to determine the strength of contractions.

Detecting the presence of meconium: Breaking the bag of waters can reveal the presence of meconium-stained amniotic fluid. If meconium is found during amniotomy, it gives the health care team time to plan appropriate measures, which will depend on the thickness of the meconium.

Before Breaking Your Bag of Waters

Before having an amniotomy to induce or augment labor, your obstetrician will explain the procedure and discuss the risks and benefits. He or she will also calculate the likelihood of the procedure being successful (Bishop's score) and make sure there are not any reasons why you should not have the procedure (contraindications).

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

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

Bishop's Score

Cervical exam 0 Points 1 Point 2 Points 3 Points
Dilation (cm) Closed 1-2 cm 3-4 cm 5-6 cm
Effacement (percent) 0-30 percent 40-50 percent 60-70 percent 80 percent
Fetal station -3 -2 -1, 0 +1, +2
Consistency Firm Medium Soft
Position Posterior Med Anterior

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), as well as its consistency and position. 

A score of 8 or more means 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.

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

The Procedure

After explaining an amniotomy and making sure your cervix is "ripe," your obstetrician or midwife will get you set up for the procedure.

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

Then, your doctor or midwife will perform a careful vaginal exam to make sure the baby's head is firmly applied to your cervix. The membranes will be snagged using an amnihook (a large device with a small sharp end, similar to a crochet hook), or an amnicot (a glove with a small sharp hook at the end of one finger). After a tear in the bag is created, the amniotic fluid will begin to flow out.

Breaking 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 at once or begin as just a small trickle. You will continue to leak fluid in small amounts for the remainder of your labor.

Once the amniotic sac has been broken, the labor team will continue to monitor you and your baby. If you want to get up and walk around, your nurse will give you a large mesh pad to catch any drainage.

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

Risks and Complications

As long as you have a favorable cervix and the baby is engaged, amniotomy has relatively few risks. Possible complications include:

  • Failure of labor to start. Labor may not begin after amniotomy and using Pitocin. However, by 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 may increase the risk of malposition which can 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 not a complication; rather, the expected "benefit" if effective, is the start and progression of labor — both of which 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).

In some cases, the detection of meconium after amniotomy and associated 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 (breathe in) meconium during delivery.

Reasons Amniotomy Should Not Be Performed

There are a few situations in which amniotomy should not be performed (contraindications). These are usually fairly obvious and can be determined by reviewing a routine ultrasound (during second trimester or later) and performing a vaginal exam. These include:

  • Abnormal presentation. If the baby is breech or in another malpresentation such as face presentation or brow presentation.
  • The baby's head is not engaged or "floating" on an exam.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. Vasa Previa can be detected on a routine ultrasound during the second trimester.

Questions to Ask Before Amniotomy

Before agreeing to have your waters broken, there are a few questions you will want to ask your doctor or midwife.

  • 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

Obstetricians have used amniotomy to stimulate labor or help it progress for more than a century. However, we aren't exactly sure of its effectiveness.

Overall, the risk is small if:

  • a routine ultrasound has been done to rule out Vasa Previa
  • the baby is well engaged
  • delivery occurs within 24 hours

When a woman has a favorable cervix, breaking the bag of waters is often used in combination with Pitocin to induce labor.

The labor intervention of amniotomy has several advantages or disadvantages. As with any medical procedure, it is important to weigh potential risks against potential benefits.

For example, 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 required when closer fetal monitoring with an internal fetal monitor and/or intrauterine pressure monitor is needed.

Every pregnancy is different. If amniotomy is considered, your doctor or midwife can take into account your medical history, the state of your cervix, and your personal preferences, to determine what is best for you and your baby.

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