High Dose vs. Low Dose Oxytocin for Labor Induction in Obese Women: a Randomized Controlled Trial - the OPS (Obese Pitocin Study) Trial
| Registry | NCT03140488, acronym OPS |
|---|---|
| Status | Completed |
| Phase | Phase 4 |
| Study type | Interventional; randomized, parallel, masking: quadruple, other |
| Enrollment | 140 (Actual) |
| Sponsor | University of Arizona (Other) |
| Conditions | Obesity, Labor, Induced, Oxytocin |
| Interventions | Oxytocin (Drug) |
| Dates | start 2017-06-05, primary completion 2018-10-12, completion 2019-09-05, first posted 2017-05-04, last updated 2022-12-20 |
| Locations | 1 site in United States |
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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.
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.
| Arm | Type | Interventions | Description |
|---|---|---|---|
| Lean-Control | Active comparator | Drug: Oxytocin | 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. |
| Lean-Intervention | Experimental | Drug: Oxytocin | 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. |
| Obese-Control | Active comparator | Drug: Oxytocin | 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. |
| Obese-Intervention | Experimental | Drug: Oxytocin | 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. |
Sex: Female, ages: 18 Years to any
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)
| Milestone | Lean-Control | Lean-Intervention | Obese-Control | Obese-Intervention |
|---|---|---|---|---|
| Started | 35 | 35 | 35 | 35 |
| Completed | 35 | 35 | 35 | 35 |
| Not completed | 0 | 0 | 0 | 0 |
Time frame: From start of oxytocin infusion until discharge from hospital after birth. We did not specify a number of days after giving birth we would collect adverse event data. However, no participants had data collected past 1 month from giving birth.
| Arm | Deaths | Serious adverse events | Other adverse events |
|---|---|---|---|
| Lean-Control | 0/35 (0.0%) | 0/35 (0.0%) | 0/35 (0.0%) |
| Lean-Intervention | 0/35 (0.0%) | 0/35 (0.0%) | 0/35 (0.0%) |
| Obese-Control | 0/35 (0.0%) | 0/35 (0.0%) | 0/35 (0.0%) |
| Obese-Intervention | 0/35 (0.0%) | 0/35 (0.0%) | 0/35 (0.0%) |
| Facility | City | Country | Status |
|---|---|---|---|
| Banner University Medical Center Tucson | Tucson, Arizona | United States |