Amniotomy

Overview

Amniotomy or artificial rupture of the membranes (AROM) is a procedure that involves intentionally breaking the amniotic sac, which is a fluid–filled sac enveloping the fetus throughout pregnancy. The rupture or breaking of the amniotic sac can induce uterine contractions, facilitating the dilation of the cervix.

The amniotic sac, also known as the bag of waters, contains a fluid called amniotic fluid. This liquid serves to safeguard and cushion the fetus, facilitating its movements within the uterus. The amniotic sac ruptures and amniotic fluid is released when the baby is ready to be born. 

For some people, this occurs naturally when the contractions intensify during childbirth. However, some may experience labor, but the amniotic sac remains intact. Amniotomy may be suggested to purposefully break water, accelerate labor, and promote cervical dilation.

Reasons for undergoing the procedure

An amniotomy may be recommended to expedite labor, but it comes with potential risks and may not be the optimal choice for everyone.

Its effectiveness is debated, with some studies indicating it may not necessarily accelerate the progress of labor in low–risk pregnancies, preferring natural progression. However, other data suggests it can accelerate labor.

AROM may be used:

• Accelerate or induce labor: Breaking the membranes can trigger the release of hormones that lead to more intense contractions. With the amniotic fluid no longer providing cushioning, your baby has the opportunity to descend further into the pelvis. This added pressure on your cervix may contribute to increased dilation.
• Assessment of amniotic fluid: Assessing the amniotic fluid for meconium aids in preparing to suction the baby’s mouth and nose as soon as they are born. The baby’s health may be impacted if they pass too much meconium, which is their first poop.
• Enhancing baby monitoring: A head–mounted internal fetal monitor provides a more accurate readout than an external one. This can help check the child’s heart rate. 

Risk

There is no certainty that an amniotomy will reduce the duration of your labor or hasten its progress. Potential complications include:

• Cesarean delivery: If the amniotic sac ruptures and the baby is in a breech position, one may be more likely to need a C–section.
• Infection: The longer the time between when the water breaks and giving birth, the higher the chance of infection for the baby. Devoid of amniotic fluid, the baby lacks protection against infections.
• Severe pain: There is no longer any cushioning between the baby’s head and the cervix once the amniotic fluid has left the body. Some patients may experience more severe contractions and severe agony.
• Umbilical cord prolapse: This may stop the oxygen from reaching the baby. This condition occurs when the umbilical cord passes through the vagina before the baby does.
• Umbilical cord compression: The supply of oxygen to the baby becomes obstructed when the umbilical cord becomes flattened. 

Before the procedure

There is no specific preparation required for an amniotomy. Pre–procedure, the healthcare provider will assess the condition of the cervix, checking for softening or thinning, and ensuring the baby’s head is properly positioned. Before an amniotomy, the ideal situation for the baby is to be low in the pelvis, exerting pressure on the cervix. Following this, pads or towels will be positioned underneath to absorb the amniotic sac fluid once it is ruptured.

Since preparation for an amniotomy is unnecessary, it is important to communicate any concerns one may have about the procedure.

During the procedure

Amniotomy or artificial rupture of the membranes (AROM) involves the use of a slender plastic instrument called an amnihook. The amnihook is inserted through the vagina. Once inside, they locate the amniotic sac or bag of water and proceed to scratch or tear a hole in it using the hook. This intentional perforation allows the amniotic fluid to be released from the sac.

Amnihook is a tool approximately 12 inches in length and features a curved hook at the top, resembling a crochet hook used for making blankets.

After the procedure

If the amniotomy is effective, the healthcare provider may inform that the cervix is dilating more rapidly than before. One may experience contractions that are more pronounced and occur at a shorter interval, including a substantial gush or a gradual trickle of fluid from the vagina. Multiple absorbent pads or towels are used to absorb the fluid.

Outcome

Amniotomy or intentionally rupturing the amniotic sac in labor has several benefits. It can hasten labor by bringing the baby nearer to the cervix and intensifying contractions. 

This procedure also enables closer monitoring of the baby for signs of distress and facilitates the assessment of meconium levels, guiding the appropriate medical support needed during delivery.