Preterm Induction of Labor Timing of Amniotomy: A Randomized Controlled Trial (PITA)

The University of Alabama at Birmingham

Status: Completed

Conditions: Labor Induction; Preterm Pregnancy

Treatments: Procedure: Early Amniotomy; Procedure: Late Amniotomy

Study type: Interventional

Funder types: Other

Identifiers

NCT03504670

UAB_EarlyAROM

Details and patient eligibility

About

Artificial rupture of membranes (amniotomy) is a commonly used technique to safely induce and augment labor. It has been shown to reduce the duration of spontaneous and induced labor in term patients (≥37 weeks' gestation). The utility of amniotomy in preterm patients (<37 weeks' gestation) undergoing medically-indicated induction of labor is unknown. However, it remains a commonly used strategy. We will conduct a trial comparing early amniotomy versus late amniotomy during medically-indicated induction of labor between 23.0 and 35.6 weeks gestation. Women will be randomized to early or late amniotomy after the obstetrician has decided to induce labor for a medical indication. We hypothesize that more women in the early amniotomy group will require cesarean delivery, and the duration of labor will increase in the early amniotomy group.

Full description

The rate of preterm birth in the United States is nearly 10%. Up to one-third of these births are the result of a medically-indicated delivery. While induction of labor in women at term gestation has been extensively studied, the same is not true for preterm gestations. Consequently, the same methods of labor induction are used in term and preterm gestations, although preterm gestations may have different responses to induction agents compared to term gestations.

At our institution, a standard induction of labor - for term or preterm women - is performed using a cervical Foley catheter or misoprostol for cervical ripening with the addition of intravenous oxytocin for labor augmentation. As membranes do not typically spontaneously rupture during the induction process, amniotomy is commonly utilized by providers to help augment labor. Amniotomy releases prostaglandin-rich amniotic fluid. These prostaglandins are important mediators of uterine contractility and ultimately active labor. It has been shown to reduce the duration of spontaneous and induced labor in term patients.

The timing of amniotomy is left up to the discretion of the treating providers, as there are no randomized controlled trials to support early versus late amniotomy at preterm gestations. However, a retrospective cohort of nulliparous and multiparous women at our institution undergoing induction at 23-34 weeks, and evaluating early amniotomy at <4cm cervical dilation versus late amniotomy at ≥4cm dilation, showed an increased risk of cesarean delivery and increased time from start of induction to delivery for early amniotomy, although only the cesarean delivery outcome was significant after adjusting for confounders.

We will conduct an intention-to-treat randomized controlled trial comparing early amniotomy versus late amniotomy during medically-indicated induction of labor between 23.0 and 35.6 weeks gestation. Women will be randomized to early or late amniotomy after the attending obstetrician has decided to induce labor for a medical indication. Early amniotomy will be performed prior to 4cm cervical dilation being reached. Late amniotomy will be performed at greater than or equal to 4cm cervical dilation.

The purpose of this study is to determine whether timing of amniotomy during medically-indicated preterm induction of labor affects labor outcomes. We will specifically be looking at risk of cesarean delivery, duration of labor, maternal morbidity, and neonatal morbidity. We hypothesize that more women in the early amniotomy group will require cesarean delivery and that the duration of labor will increase in the early amniotomy group.

Enrollment: 86 patients

Sex: Female

Ages: 18+ years old

Volunteers: No Healthy Volunteers

Inclusion criteria

• Singleton gestation
• Gestational age at randomization between 23.0 and 35.6 weeks
• Induction of labor planned for maternal or fetal indications
• Reassuring fetal status
• Vertex presentation

Exclusion criteria

• Plan for cesarean delivery or contraindication to labor
• Cervix ≥4cm dilated at start of induction
• Signs of spontaneous labor (active contractions with cervical change)
• Ruptured membranes
• Chorioamnionitis
• Intrauterine fetal demise
• Known major fetal anomaly
• Participation in any other clinical trial involving the course of labor
• Maternal hepatitis B, C, or HIV infection (or unknown status)
• Deferring intrapartum fetal monitoring and/or cesarean section for any reason (for example, after periviability counseling)

Trial design

Primary purpose: Treatment

Allocation: Randomized

Interventional model: Parallel Assignment

Masking: None (Open label)

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86 participants in 2 patient groups

Early amniotomy

Experimental group

Description:

Women randomized to early amniotomy will have their membranes ruptured in usual fashion using an amniotomy hook when the cervix is less than 4cm dilated. This will occur after cervical ripening has taken place, with 1) a cervical Foley balloon catheter with or without oxytocin and/or 2) misoprostol. Prior to amniotomy, the obstetric provider will assess whether or not the fetal head is engaged. If the fetal head is not engaged (applied to the cervix), amniotomy will be deferred. The patient will be examined every 2 hours until amniotomy can be safely performed (in keeping with our institutional standard of care to examine women every 2-4 hours in labor).

Treatment:

Procedure: Early Amniotomy

Late amniotomy

Experimental group

Description:

Women randomized to late amniotomy will have their membranes ruptured once the cervix reaches at least 4cm dilation. This will occur after cervical ripening has taken place, with 1) a cervical Foley balloon catheter with or without oxytocin and/or 2) misoprostol. If the cervix fails to reach 4cm dilation 12 hours following cervical ripening, amniotomy will be performed.

Treatment:

Procedure: Late Amniotomy