First Obstetrics and Gynecology Special
“Delivery Room Skill Learning Session”
Practical Skills, Comprehensive Analysis
-First Issue-
Artificial Rupture of Membranes
In the delivery room, we often hear, “This patient has a poor fetal heart rate, prepare for an emergency cesarean section.” In fact, in response to fetal distress, depending on the urgency and the reason, the usual first step taken in today’s delivery room is
Artificial Rupture of Membranes (ARM), commonly known as “breaking the water,” is an intervention to artificially tear the amniotic membrane at the cervical opening to observe the color of the amniotic fluid, enhance uterine contractions, and accelerate labor progress. It is a common induction method during natural childbirth.
1. History of ARM and Scholars’ Understanding
ARM has been used in obstetric clinical practice since the 11th century, as documented in literature. By the end of the 20th century, some scholars began to question the surgical method of ARM, leading to different viewpoints. Obstetricians have reached a consensus that this invasive procedure is no longer considered a necessary intervention in the labor process.
2. Clinical Applications of ARM
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Inducing Contractions – Labor Induction
01 ARM Induction
Indications for Use:
(1) Conditions for vaginal trial of labor induction (IOL) are met. (2) Bishop score of the cervix ≥ 7 points.
Relative Contraindications: (1) Fetal head not engaged in the pelvis. (2) Fetal head not firmly against the cervix. The standard operating procedure for ARM is shown in Figure 1.
02 Performing ARM after Balloon Catheter for Cervical Ripening
ARM is more often used after inducing regular contractions using medication or mechanical methods. For instance, if the Bishop score is ≤ 6, place a balloon catheter for induction, remove the balloon after 12 hours, and it is recommended to immediately administer oxytocin after ARM; if the balloon fails to effectively ripen the cervix, or if ARM cannot be performed, sequential use of dinoprostone can be employed for cervical ripening, or the cervical balloon can be reinserted after 24 hours.
Currently, some scholars in China believe that after ARM, observation should last 30-60 minutes, and if contractions do not strengthen, a small dose of oxytocin can be used again.
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Shortening Labor – Augmentation
01 Routine ARM during Labor is Not Recommended
The 2020 Clinical Practice Guidelines for Normal Labor established by the Obstetrics Group of the Chinese Medical Association and the Perinatal Medicine Group clearly state that routine ARM during labor is not recommended.
02 ARM in Active Phase is Recommended, Not During Latent Phase
ARM is generally performed when the cervix is ≥ 5 cm dilated. If after ARM there is a lack of effective contractions, oxytocin can be used to promote labor progress. The method of combining ARM with intravenous oxytocin can shorten the time from induction to delivery. If the membranes remain intact after full dilation and fetal descent is affected, ARM can be performed during contraction intervals to facilitate fetal descent and manual rotation of the fetal head.
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Adjusting Fetal Position (ARM + Manual Rotation)
For pregnant women with abnormal fetal positions, after entering the second stage of labor or when the cervix is nearly fully dilated, when the biparietal diameter of the fetal head reaches the level of the ischial spines or lower, manual rotation of the fetal position after ARM is the main corrective measure.
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ARM for Vaginal Birth After Cesarean Section (VBAC)
In 2019, Wingert et al. systematically reviewed and meta-analyzed literature published between 1985 and 2019 on VBAC induction methods and delivery outcomes in English and French. The results showed that there was no difference in VBAC success rates between ARM and spontaneous labor (RR 1.06, 95% CI 0.88-1.28). These studies assessed the vaginal delivery rates for VBAC, all lacking high-quality evidence to support that ARM can increase the vaginal delivery rate for VBAC.
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ARM for Twin Vaginal Delivery
It is not recommended to perform ARM during the first stage of labor. In our clinical practice, the ideal interval between the delivery of two fetuses is 5-10 minutes. After the first fetus is delivered, quickly stabilize the second fetus in a longitudinal position. If the presenting part is a foot, the second fetus can be grasped by the ankle through the relaxed cervix, pulling it to the vaginal opening during contraction intervals. After ARM, breech delivery or breech extraction can be performed; if the second fetus is head down, an assistant can gently push down on the fundus of the uterus, and once the fetal head is engaged, ARM can be performed during contraction intervals to deliver the fetus. After the first fetus is delivered, oxytocin should be administered appropriately based on contraction status.
3. Special Situations for ARM
01 HSV Infection and ARM
The risk of vertical transmission of genital HSV infection from mothers to newborns during vaginal delivery is 30%-50%. Even in asymptomatic cases, invasive procedures during labor (ARM, forceps, surgical assistance, etc.) should be minimized to reduce the time the fetus is exposed to vaginal secretions and decrease the likelihood of fetal viral infection.
02 Group B Streptococcus (GBS) Infection and ARM
Evidence suggests that ARM does not increase the risk of early-onset GBS infection in newborns (evidence level: D). Any pregnant woman with GBS isolated from urine at any stage of pregnancy should receive intrapartum antibiotic prophylaxis (IAP), without the need for late pregnancy GBS screening. All other pregnant women should undergo vaginal and rectal GBS screening at 35-37 weeks of gestation. Except for cesarean sections performed with intact membranes, all GBS-positive pregnant women should receive IAP at the time of delivery or membrane rupture. The optimal timing for IAP is 4 hours before delivery, and unless there is a GBS urinary tract infection, antibiotics should not be used to eliminate GBS colonization from the genital tract or rectum before delivery (evidence level: expert consensus).
>>>> Indications for Prophylactic Antibiotic Use for GBS during Labor Include:
(1) Positive prenatal GBS screening (AII).
(2) GBS bacteriuria during pregnancy (AII).
(3) History of GBS infection in newborns during previous deliveries (AII).
(4) Unknown GBS colonization status with any of the following conditions (AII):
① Preterm labor;
② Premature rupture of membranes > 18 hours;③ Maternal fever ≥ 38℃;④ Positive GBS nucleic acid amplification test during labor;⑤ History of positive GBS in previous pregnancies.
03 Hepatitis Virus Infection and ARM
The 2017 WHO clinical guidelines state that in areas with high prevalence of hepatitis virus infection among pregnant women, efforts should be made to maintain membrane integrity to prevent vertical transmission from mother to child. During delivery, if the newborn has been “immersed” in virus-containing fluids, care should be taken to gently clean the newborn’s mouth and nasal cavity to avoid excessive force that could cause mucosal injury and introduce the virus into the newborn’s body.
04 HIV Infection and ARM
The UK HIV Association’s 2019 guidelines for managing HIV during pregnancy and postpartum state that if the HIV viral load is <50 copies/mL, invasive prenatal diagnostic testing may be performed. Pregnant women with ruptured membranes close to delivery, if their viral load is low, may undergo a vaginal trial of labor, aiming to deliver within 24 hours of rupture.
4. Precautions for ARM Operation and Emergency Handling of Cord Prolapse
01 Emergency Handling of Cord Prolapse After ARM
One of the important complications of ARM is cord prolapse. Most cases of cord prolapse occur within minutes after membrane rupture; one study found that 57% occurred within 5 minutes and 67% within 1 hour post-rupture. If fetal heart rate deceleration or variable decelerations occur within minutes after ARM, especially if abnormal fetal heart monitoring occurs immediately after rupture, one should be vigilant for possible cord prolapse. If cord prolapse is diagnosed, vaginal delivery is not possible in the short term, and an immediate cesarean section should be performed. If bloody amniotic fluid is present after ARM, with or without abnormal fetal heart rate, there is a high suspicion of placental abruption.
In summary, the clinical applications of ARM are:
(1) When the cervix is not mature and the Bishop score is ≤ 6, simple ARM not only has a low success rate for induction but also cannot predict the timing of delivery, and the prolonged time from rupture to delivery may lead to infection; thus, it is not recommended to use ARM alone for cervical ripening. When the cervix is mature, with a Bishop score ≥ 7, ARM can be combined with oxytocin for induction.
(2) In cases of previous cesarean section and Bishop score ≤ 6, place a balloon catheter for induction, remove it after 12 hours, and administer oxytocin immediately after ARM. If the balloon does not effectively ripen the cervix, sequential use of dinoprostone can be employed for cervical ripening, or the cervical balloon can be reinserted after 24 hours.
(3) The 2020 Normal Labor Guidelines clearly state that routine ARM during labor is not recommended. (4) ARM during the latent phase is not encouraged; if there are indications for ARM, it is recommended to perform it during the active phase.
(4) In special situations, ARM must have indications; all GBS-positive pregnant women should receive IAP at the time of delivery or membrane rupture.
When performing ARM, emphasize the “Three Musts”: there must be indications, a medical order, and documentation, and it must be executed after good communication with the patient and their family.
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Source: Midwife’s Notes
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