High- vs low-dose oxytocin in lean and obese women: a double-blinded randomized controlled trial

High- vs low-dose oxytocin protocols for labor induction: a systematic review and meta-analysis

OBJECTIVE

This systematic review aimed to synthesize available literature reporting maternal and neonatal outcomes of induction of labor using high- vs low-dose oxytocin protocols.

DATA SOURCES

PubMed, Embase, Scopus, CINAHL, and Cochrane databases and ClinicalTrials.gov were searched from inception to January 17, 2023.

STUDY ELIGIBILITY CRITERIA

Studies with the following criteria were included: randomized or observational studies conducted with pregnant individuals, published in English, that compared low-dose (starting dose 0.5-2 milliunits/min increased by 1-2 milliunits/min every 15-40 min) versus high-dose (≥4 milliunits/min increased by 3-6 milliunits/min every 15-40 min) oxytocin infusion protocols for induction of labor. Studies of individuals with fetal death were excluded.

STUDY APPRAISAL AND SYNTHESIS METHODS

Two reviewers independently extracted data and appraised study quality following the PRISMA guidelines and using the Cochrane risk of bias assessment tools. The primary outcome was cesarean delivery. Secondary outcomes included spontaneous vaginal delivery, operative vaginal delivery, duration of labor induction, uterine tachysystole, and maternal and neonatal morbidity outcomes. Pooled relative risks (RR) with 95% confidence intervals [CI] were calculated using random-effects models. Heterogeneity was assessed statistically using the Higgins' I2 test and visually using a funnel plot.

RESULTS

Six studies (two randomized controlled trials, four observational studies) were included, encompassing 7,850 deliveries (3,957 in the high-dose group and 3,893 in the low-dose group). Overall, there was no difference in the risk of cesarean delivery following induction of labor with a high-dose oxytocin protocol compared with a low-dose protocol (26.0% vs 28.4%, pooled RR 1.02, 95% CI 0.85-1.21). There were also no differences in the likelihood of cesarean delivery for non-reassuring fetal status or neonatal morbidity, or in the duration of labor. Induction with high-dose oxytocin was associated with a lower frequency of postpartum hemorrhage, compared with a low-dose protocol (7.6% vs 9.9%, RR 0.78, 95% CI 0.66-0.92). Details of high- and low-dose protocols varied widely between studies, which all were at medium or high risk of bias. There was moderate heterogeneity (I2 = 45.5%), and no evidence of publication bias (Harbord test, p=0.74).

CONCLUSIONS

A synthesis of the existing literature demonstrates no difference in the frequency of cesarean delivery following induction of labor using a high- vs low-dose oxytocin protocol. However, this review highlights the methodological limitations of the few available published studies and the need for high-quality trials to guide optimal oxytocin dosing for labor induction.

High-Dose versus Low-Dose Oxytocin for Labor Augmentation: A Meta-Analysis of Randomized Controlled Trials

Background/Objectives: Although oxytocin administration is recommended for delayed labor progress, there is no consensus over the preferred optimal dose of oxytocin. We aimed to perform a meta-analysis of pregnancy outcomes comparing high-dose versus low-dose oxytocin regimens for augmentation of delayed labor. Methods: PubMed, Embase, and Cochrane databases were systematically searched for studies comparing high-dose with low-dose oxytocin for labor augmentation from inception up to May 2023. The outcomes assessed were cesarean rate, instrumental delivery rate, postpartum hemorrhage, neonatal death, and uterine tachysystole. Subgroup analysis was performed with randomized controlled trials (RCTs) and propensity-matched studies. Statistical analysis was performed using Rstudio. Heterogeneity was assessed with I2 statistics, and a random-risk effect was used if I2 > 50%. Results: Twenty-one studies met inclusion criteria, and eighteen were RCTs. A total of 14.834 patients were included, of whom 7.921 (53.3%) received high-dose and 6.913 (46.6%) received low-dose oxytocin during labor augmentation. No statistical differences were found in cesarean delivery, neonatal mortality, postpartum hemorrhage and vaginal instrumentation rate. However, uterine tachysystole incidence was significantly higher with high-dose oxytocin (95% Cl, 1.30-1.94, p = 0.3; 0.6; I2 = 9%). Conclusions: Labor augmentation with a low-dose oxytocin regimen is effective as with a high-dose regimen, but with significantly less uterine tachysystole events, which can lead to intrauterine and neonatal complications. Our findings suggest that a low-dose regimen may be safe and effective for labor augmentation in medical practice.

Weight-based versus fixed dose oxytocin infusion for preventing uterine atony during cesarean section in laboring patients: A randomized trial

OBJECTIVE

We compared efficacy of weight-based (0.4 IU/kg/h) versus fixed-dose (34 IU/h) oxytocin infusion during cesarean section.

METHODS

The oxytocin infusion in either group (n = 32 each) was initiated upon cord clamping. Primary outcome measure was adequacy of uterine tone at 4 min after initiating oxytocin infusion. Oxytocin associated side effects were also observed.

RESULTS

Significantly less oxytocin was used with the weight-based versus fixed-dose regimen (16.3 [11.2-22.4] IU vs 20.4 [15.8-26.9] IU; P = 0.036). Incidence of adequate uterine tone was clinically greater but not significantly different with the weight-based versus fixed-dose regimen (81.3% vs 71.9%; P = 0.376). The weight-based regimen was associated with clinically lesser, although not statistically significant need for rescue oxytocin (25% vs 46.9%; P = 0.068) and additional uterotonic (9.4% vs 15.6%; P = 0.708); as well as oxytocin associated side effects (hypotension [34.4% vs 46.9%; P = 0.309], nausea/vomiting [18.8% vs 40.6%; P = 0.055], and ST-T changes [0% vs 3.1%; P = 1.000]).

CONCLUSION

Weight-based oxytocin was not significantly different from the fixed-dose regimen in terms of uterotonic efficacy or associated side-effects, despite significantly lower doses being used. Use of weight-based oxytocin infusion (0.4 IU/kg/h) can be considered in clinical practice.

TRIAL REGISTRATION

Clinical Trial Registry of India (ctri.nic.in, number. CTRI/2021/01/030642).

Oxytocin: physiology, pharmacology, and clinical application for labor management

Oxytocin is a peptide hormone that plays a key role in regulating the female reproductive system, including during labor and lactation. It is produced primarily in the hypothalamus and secreted by the posterior pituitary gland. Oxytocin can also be administered as a medication to initiate or augment uterine contractions. To study the effectiveness and safety of oxytocin, previous studies have randomized patients to low- and high-dose oxytocin infusion protocols either alone or as part of an active management of labor strategy along with other interventions. These randomized trials demonstrated that active management of labor and high-dose oxytocin regimens can shorten the length of labor and reduce the incidence of clinical chorioamnionitis. The safety of high-dose oxytocin regimens is also supported by no associated differences in fetal heart rate abnormalities, postpartum hemorrhage, low Apgar scores, neonatal intensive care unit admissions, and umbilical artery acidemia. Most studies reported no differences in the cesarean delivery rates with active management of labor or high-dose oxytocin regimens, thereby further validating its safety. Oxytocin does not have a predictable dose response, thus the pharmacologic effects and the amplitude and frequency of uterine contractions are used as physiological parameters for oxytocin infusion titration to achieve adequate contractions at appropriate intervals. Used in error, oxytocin can cause patient harm, highlighting the importance of precise administration using infusion pumps, institutional safety checklists, and trained nursing staff to closely monitor uterine activity and fetal heart rate changes. In this review, we summarize the physiology, pharmacology, infusion regimens, and associated risks of oxytocin.

Vaginal Compared With Oral Misoprostol Induction at Term: A Cluster Randomized Controlled Trial

OBJECTIVE

To evaluate efficacy in achieving vaginal delivery with a standardized vaginal compared with oral misoprostol regimen for labor induction at term.

METHODS

In this single-center, cluster randomized trial, we randomized induction method by week among individuals with gestational age of 37 weeks or more, cervical dilation of 2 cm or less, intact membranes, and indication for delivery to either oral (100 micrograms every 4 hours for up to two doses), or vaginal (25 micrograms every 3 hours for up to five doses) misoprostol regimens, followed by a standardized oxytocin protocol. Individuals with an antepartum stillbirth, major fetal anomalies, malpresentation, ruptured membranes, nonreassuring fetal status, or contraindication to prostaglandin were excluded. The primary outcome was vaginal delivery at first induction attempt. Secondary outcomes included time to delivery, need for oxytocin, chorioamnionitis, and adverse maternal and neonatal outcomes. Outcomes were recorded at the individual level and adjusted for clustering, with analysis by intention to treat.

RESULTS

Between May 24, 2021, to September 19, 2022, 1,322 women were randomized to vaginal misoprostol in 33 clusters and 1,224 to oral misoprostol in 37 clusters. Demographic characteristics or initial cervical dilation did not differ between groups. The primary outcome did not differ between induction regimens and occurred in 1,032 (78.1%) of the vaginal misoprostol arm and 945 (77.2%) of the oral misoprostol arm (adjusted relative risk [RR] 1.01, 95% CI, 0.97-1.05). Tachysystole with fetal heart rate changes occurred less frequently with vaginal compared with oral misoprostol (3.5% vs 5.9%, adjusted RR 0.59, 95% CI, 0.40-0.87). Time to delivery did not differ between groups. Oxytocin was less frequently required before delivery in the vaginal misoprostol group (68.8% vs 78.4%, adjusted RR 0.88, 95% CI, 0.84-0.92).

CONCLUSION

Induction of labor with vaginal compared with oral misoprostol protocols did not increase the frequency of vaginal delivery at term but did reduce the need for oxytocin use before delivery.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov, NCT04755218.