Oxytocin Dosage to Decrease Induction Duration (OPS)

High Dose vs. Low Dose Oxytocin for Labor Induction in Obese Women: a Randomized Controlled Trial - the OPS (Obese Pitocin Study) Trial

This is a randomized controlled trial in which women are allocated either 'high dose' or 'low dose' oxytocin infusions for induction of labour. The randomization is stratified by maternal body mass index.

Study Overview

• Status: Completed
• Conditions: Obesity; Oxytocin; Labor, Induced
• Intervention / Treatment: Drug: Oxytocin

Detailed Description

Obesity is considered a major public health concerns and increases the risk of many comorbid medical conditions. Obesity in pregnancy places women at higher risk of obstetrical complications during pregnancy, delivery and postpartum. In particular, obese pregnant women have more difficulty going into labor, a longer labor course, and even with pharmacologic treatment, have a higher chance of requiring cesarean delivery.

When pregnant women need help going into labor, they commonly receive a medication called Pitocin on the labor and delivery floor. Pitocin is the brand name and is a synthetic analog to the naturally produced oxytocin, a hormone secreted by mother when they naturally go into labor. This medication has been used widely around the world. There is emerging evidence that obese women need more oxytocin to go into labor compared to their lean cohorts. There are many studies to support the use of different oxytocin dosage protocols (both high and low dose infusion increments). Despite these evidences, a low dose oxytocin regimen is universally used in the United States, regardless of patient characteristics.

This study is a double blinded randomized controlled trial. Both lean and obese cohorts will be recruited for the study. The investigators will randomly place both cohorts into the low or the high dose oxytocin regimen treatment group. The investigators, patients and providers will be blinded and will not know the specific assignments. The purpose of this study is to evaluate the effect of high dose oxytocin in the obese cohort. The hypothesis is that obese patient will have shorter time to delivery with the high dose oxytocin regimen without incurring any additional risks or adverse outcomes.

• Study Type: Interventional
• Enrollment (Actual): 140
• Phase: Phase 4

Contacts and Locations

Study Locations

• United States
  • Arizona
    • Tucson, Arizona, United States, 85724
      • Banner University Medical Center Tucson

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 14 years and older (Adult, Older Adult)
• Accepts Healthy Volunteers: No
• Genders Eligible for Study: Female

Description

Inclusion Criteria:

• Singleton pregnancy ≥ 37 weeks gestation
• Patient presented for induction of labor who is determined to be a candidate for oxytocin
• Cephalic presentation
• Reassuring fetal health assessment (no abnormal findings in fetal assessment, see below)
• Meeting one of the following BMI category:

Obese group: BMI ≥30 at <20 weeks of pregnancy, or BMI ≥35 at a term gestation of pregnancy Lean group: BMI ≤25 at <20 weeks of pregnancy, or BMI ≤28 at a term gestation of pregnancy

Exclusion Criteria:

• Non-reassuring fetal assessment at the time of recruitment
• Previous cervical ripening agents (cytotec, cervidil, cervical Foley Balloon)
• <18 years of age
• Prisoners
• Any patients contraindicated for vaginal delivery
• Multiple gestations
• History of previous cesarean delivery
• Patients with history of significant cardiac disease
• Fetal demise
• Estimated fetal weight greater than 4500 grams in diabetic and 5000 grams in non-diabetic mother
• Ruptured membranes
• Spontaneous labor (latent or active phase)
• Augmentation of labor (latent or active phase)

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Other
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Quadruple

Number of Arms

4

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Active Comparator: Lean-Control; 1) Control group: Lean cohort: BMI ≤25, at <20 weeks gestation or BMI ≤28 at a term gestation, low dose oxytocin protocol Low dose oxytocin regimen (the standard at Banner University Labor and Delivery, as well as across the United States): 30 units in 500cc 0.9% normal saline bag (60 milliunit/cc). Starting rate would be 2 milliunit/minute, or 2cc/hour. The medication will be increased by 2 milliunit/minute = 2cc/hr every 30 minutes until adequacy of contraction or cervical change. At 20 milliunit/minute = 20cc/hr, provider will assess patient for eligibility to continue to increase oxytocin dosage.	Drug: Oxytocin; Patients will be randomized to low dose or high dose oxytocin for induction of labor.; Other Names: Pitocin; Syntocinon
Experimental: Lean-Intervention; 2) Intervention group: Lean cohort: BMI ≤25, at <20 weeks gestation or BMI ≤28 at a term gestation, high dose oxytocin protocol High dose oxytocin regimen (endorsed by American College of Obstetricians and Gynecologists): 90 units in 500cc 0.9% normal saline bag (180 milliunit/cc). Starting rate would be 6 milliunit/minute, or 2cc/hour. The medication will be increased by 6 milliunit/minute = 2cc/hr every 30 minutes until adequacy of contraction or cervical change. At 60 milliunit/minute = 20cc/hr, provider will assess patient for eligibility to continue to increase oxytocin dosage.	Drug: Oxytocin; Patients will be randomized to low dose or high dose oxytocin for induction of labor.; Other Names: Pitocin; Syntocinon
Active Comparator: Obese-Control; 3) Control group: Obese cohort: BMI ≥30, at <20 weeks gestation or BMI ≥35 at a term gestation, low dose oxytocin protocol Low dose oxytocin regimen (the standard at Banner University Labor and Delivery, as well as across the United States): 30 units in 500cc 0.9% normal saline bag (60 milliunit/cc). Starting rate would be 2 milliunit/minute, or 2cc/hour. The medication will be increased by 2 milliunit/minute = 2cc/hr every 30 minutes until adequacy of contraction or cervical change. At 20 milliunit/minute = 20cc/hr, provider will assess patient for eligibility to continue to increase oxytocin dosage.	Drug: Oxytocin; Patients will be randomized to low dose or high dose oxytocin for induction of labor.; Other Names: Pitocin; Syntocinon
Experimental: Obese-Intervention; 4) Intervention group: Obese cohort: BMI ≥30, at <20 weeks gestation or BMI ≥35 at a term gestation, high dose oxytocin protocol High dose oxytocin regimen (endorsed by American College of Obstetricians and Gynecologists): 90 units in 500cc 0.9% normal saline bag (180 milliunit/cc). Starting rate would be 6 milliunit/minute, or 2cc/hour. The medication will be increased by 6 milliunit/minute = 2cc/hr every 30 minutes until adequacy of contraction or cervical change. At 60 milliunit/minute = 20cc/hr, provider will assess patient for eligibility to continue to increase oxytocin dosage.	Drug: Oxytocin; Patients will be randomized to low dose or high dose oxytocin for induction of labor.; Other Names: Pitocin; Syntocinon

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Length of Time to Delivery	Number of minutes from induction of labor with oxytocin infusion to delivery of infant, no maximum amount of time specified.	Start of induction to Delivery

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Maximum Oxytocin Infusion Rate	rate measured in milliunits/minute during induction of labour, no time limit applied.	Start of induction to Delivery
Number of Participants With Terbutaline Use	If terbutaline was injected during labor to decrease number or strength of contraction	Start of induction to Delivery
Rate of Cesarean Delivery	total number of patients who undergo cesarean delivery	Start of induction to Delivery
Rate of Cesarean Delivery for Labor Arrest	Number of patients who undergo cesarean delivery due to labor arrest/ failed induction	Start of induction to Delivery
Maternal Blood Loss	Blood loss in milliliters	At delivery
Number of Neonates With Apgar Score <7	5 minute Apgar Score <7 *Apgar is an acronym for which each criterion is given a minimum of 0 and maximum of 2 points: Appearance (skin color), Pulse (heart rate), Grimace (reflex irritability), Activity (muscle tone), Respiration	5 minutes after birth

Collaborators and Investigators

• Sponsor: University of Arizona
• Investigators: Principal Investigator: Meghan Hill, MBBS, University of Arizona

Publications and helpful links

General Publications

• Wei RM, Bounthavong M, Hill MG. High- vs low-dose oxytocin in lean and obese women: a double-blinded randomized controlled trial. Am J Obstet Gynecol MFM. 2022 Jul;4(4):100627. doi: 10.1016/j.ajogmf.2022.100627. Epub 2022 Mar 28.

Study record dates

Study Major Dates

• Study Start (Actual): June 5, 2017
• Primary Completion (Actual): October 12, 2018
• Study Completion (Actual): September 5, 2019

Study Registration Dates

• First Submitted: April 19, 2017
• First Submitted That Met QC Criteria: May 2, 2017
• First Posted (Actual): May 4, 2017

Study Record Updates

• Last Update Posted (Estimate): December 20, 2022
• Last Update Submitted That Met QC Criteria: November 28, 2022
• Last Verified: November 1, 2022

More Information

Terms related to this study

• Keywords: BMI; Induction of labor; Pitocin
• Additional Relevant MeSH Terms: Physiological Effects of Drugs; Reproductive Control Agents; Oxytocics; Oxytocin
• Other Study ID Numbers: 1702231223

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: No

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: Yes
• Studies a U.S. FDA-regulated device product: No
• product manufactured in and exported from the U.S.: Yes