Manual breaking of the water, or artificial rupture of the fetal membranes (AROM), is a common, routine procedure in obstetrics. Its main intentions are to induce the onset of labor or increase contractions and speed up spontaneous labor. AROM has a few benefits but also some risks.
Artificial Rupture of Membranes
Also referred to as an amniotomy or breaking the bag of waters, facts about artificial rupture of membranes include:
- It is a quick and relatively easy procedure in experienced hands.
- There is little discomfort to the mother, so no anesthesia is used.
- It is usually done when the cervix is somewhat effaced and has progressed to at least three centimeters dilation.
- In many places around the world, it is done routinely on all women at some point during active labor or if labor is slow.
Reasons for the Procedure
The reasons for performing artificial rupture of membranes include the following:
- To induce the onset of labor: Doctors and midwives often break the bag of waters as one of the methods used for induction of labor. It is thought that AROM releases prostaglandins and other chemicals from the fetal membranes, which trigger the onset of labor.
- To augment labor: AROM is often done when spontaneous labor is not progressing as quickly as expected. The release of fetal membrane chemicals might strengthen contractions and hasten labor.
- To attach a fetal scalp electrode: An electrode is attached to the baby's head for internal monitoring of the fetal heart rate. This is done when closer monitoring of the baby is needed, or the external abdominal electrode information is not reliable.
- Intrauterine pressure catheter placement: Sometimes this is needed to more effectively measure the pressure in the uterine cavity during contractions. An intrauterine pressure catheter (IUPC) is usually placed when high doses of pitocin are used to stimulate contractions.
At some point during labor if the amniotic sac is still intact, it has to be broken to progress through the second (pushing) stage of labor to get the baby out of the vagina.
Performing the Amniotomy
To decrease the risk of cord prolapse during the procedure, the fetal head should be engaged in the pelvis and applied to the cervix. The amniotomy is done under sterile conditions to reduce the chance of introducing infection into the uterus.
To break the bag of waters, many doctors use a sterile amniohook - a special instrument that resembles a long crotchet hook. Alternate tools include:
- The amnioglove - a small hook on the end of a finger of a sterile glove
- The amniocot - a one-finger "glove" that slides over a finger of the doctor's sterile glove.
- A finger - It is sometimes easy just to poke a finger into the amniotic sac if the waters are bulging through the opening of the cervix.
During the procedure, the pregnant woman lies on her back in her labor bed with knees bent and legs frog-legged out to the sides. When using the amniohook, the doctor takes the following steps after preparing the patient:
- With sterile gloves on, she inserts two fingers in the vagina similar to a routine vaginal exam.
- Once the doctor locates the cervix, she puts her finger tips just through the entrance so she can touch the bag of waters.
- She passes the amniohook into the vagina, guiding it along her fingers to the amniotic sac of waters.
- With her other hand, the doctor manipulates the hook to snag a hole in the bag of waters, taking care not to injure the baby.
- The doctor checks around the cervix to ensure the umbilical cord is not prolapsed through it.
- Medical staff monitors the fetal heart rate closely for the next 20 to 30 minutes.
As a result of the amniotomy, the amniotic fluid (the waters) pours out, and the baby's head might descend further. The procedure is easier if the bag of waters is bulging through the cervix.
Benefits of breaking the water include:
- It allows for closer monitoring of the baby and contractions by being able to place a fetal scalp electrode or an intrauterine pressure catheter, if needed.
- The doctor is able to see if the amniotic fluid has meconium (the baby's first stool) in it and take action. Passage of meconium can be a sign of fetal distress. If the baby inhales the meconium, it puts her at risk for death in-utero or major respiratory difficulties at birth.
- The doctor might also detect if there are signs of infection, such as a murky or bad-smelling amniotic fluid.
There are a few risks to an amniotomy, including:
- If the baby's head is not well-engaged in the pelvis before AROM, as the water gushes out, the umbilical cord can descend and be compressed by part of the baby. The cord might also prolapse into the vagina. Both situations can cut off the baby's oxygen supply.
- Similarly, when the head is not engaged before rupture of membranes, there is a possibility the baby might turn to a breech position after, which is a more risky birth position.
- The fetal heart rate can drop as a result of the procedure.
- There is a small risk of laceration of the fetal scalp resulting in bleeding.
- It increases the likelihood other interventions will follow, including an increased chance of a cesarean birth.
- There is a small risk of introducing infection in the uterus if sterile technique is not used.
Once the amniotic sac is broken, there is also an increased risk of maternal and fetal infection from vaginal bacteria if delivery is prolonged more than 24 hours.
Research on Amniotomy to Speed Labor
There is debate about whether AROM speeds up spontaneous labor. In a 2013 report of a Cochrane Systematic Review of research studies, based on the outcome of the 5,583 pregnancies the researchers found:
- Routine amniotomy did not speed up the progress of the first stage of spontaneous labor.
- There were no improvements in the condition of the newborns or in the women's satisfaction with their birth experience compared to women without amniotomies.
- The evidence did not support the routine use of amniotomy in the management of labor.
ACOG Committee Opinion
Based on the Cochrane Review and other data, the American College of Obstetricians and Gynecologists (ACOG) issued a Committee Opinion in February 2017. ACOG recommended against the routine use of amniotomy in low risk pregnancies where labor is progressing without problems. This opinion on artificially breaking the waters is part of ACOG's less-intervention-is-better recommendations.
The practice of AROM to try to speed labor is slow to change mainly because of its long tradition of easy and relatively safe use in obstetrics. Still, it is a valuable procedure when internal fetal heart rate or intrauterine pressure monitoring is needed or to check for passage of meconium by a fetus in distress.
Talk With Your OB Provider
When you talk about your birth plan with your OB doctor or midwife, include a discussion of the possible use of amniotomy during your childbirth. You will be more prepared to deal with the pros and cons if she/he recommends breaking your waters while you are in labor.