While a moderate increase of postpartum hemorrhage (PPH) risk is observed based on oxytocin dosage, the use of oxytocin augmentation is not associated with PPH and blood loss risk compared to patients with similar obstetric characteristics, according to a recent study published in the American Journal of Obstetrics & Gynecology.
Takeaways
- While there is a moderate increase in postpartum hemorrhage (PPH) risk associated with oxytocin dosage, the study indicates that this risk is not significantly higher compared to patients with similar obstetric characteristics who did not receive oxytocin augmentation.
- Previous concerns regarding the association between increased oxytocin use and rising PPH incidence have been based on limited data, often confounded by common occurrences of labor dystocia in patients utilizing oxytocin.
- The study conducted a retrospective observational analysis of a substantial cohort comprising 228,562 deliveries between 2002 and 2008. This large-scale approach allowed for robust evaluation of the association between oxytocin use and PPH risk.
- To ensure consistency in labor management and data structure, participants were selected from 5 hospitals within Intermountain Healthcare, Utah. Oxytocin was administered using a pump infusion system, and eligibility criteria were strictly defined to include only singleton gestations, vertex presentation, term births, and spontaneous labor onset.
- Despite observing a gradual increase in PPH and estimated blood loss (EBL) risks with oxytocin duration and dosage, the study found no clinically significant association between oxytocin use for augmentation and PPH or EBL when compared to women with similar obstetrical characteristics who did not receive oxytocin augmentation.
Approximately 3% to 5% of obstetrical patients experience PPH, and data has indicated rising incidence in the past 2 to 3 decades. Oxytocin use has also risen, with over 50% of women utilizing oxytocin for labor induction or augmentation. This has led to concerns about a potential association between increased oxytocin use and increased PPH incidence.
Data about the association between oxytocin use and PPH risk has remained limited by labor dystocia being common in patients utilizing oxytocin, which may have caused cofounding by indication. Therefore, and analysis utilizing real-world data is necessary to evaluate this association.
Investigators conducted a retrospective observational study evaluating 228,562 deliveries between 2002 and 2008. Data was obtained from electronic medical records and included medical history, maternal demographic characteristics, labor and delivery summary, reproductive and prenatal history, and postpartum and newborn information.
Participants were selected from 5 hospitals from Intermountain Healthcare, Utah, to allow for consistency of labor management and data structure in the analysis. Oxytocin was delivered to patients through a pump infusion system. Starting doses were 1, 2, or 4 milliunits per minute of oxytocin.
Eligibility criteria included singleton gestation, vertex presentation, term birth, and spontaneous labor onset. Women with prior uterine scars were excluded from the analysis. Variables included medical history, maternal demographic characteristics, postpartum and newborn information, cervical dilation, fetal station, effacement, and oxytocin dose.
PPH was the primary outcome of the analysis, determined based on recorded PPH in electronic medical records and an International Classification of Diseases, Ninth Revision PPH code. Estimated blood loss (EBL) was reported as a secondary outcome.
There were 20,889 women with spontaneous onset of labor included in the analysis, 2.3% of whom had PPH and 46.4% received oxytocin for augmentation. Nulliparous status was reported in 50.7% of women who received oxytocin vs 36.3% who did not receive oxytocin.
Epidural analgesia was reported in 95.6% of women who received oxytocin. These women had a median cervical dilation at admission of 3 cm, compared to 4 cm among women who did not receive oxytocin. A median cervical effacement of 80% vs 90%, respectively, was observed. Finally, women with oxytocin had an increased EBL of 38 mL at admission.
A correlation was seen between duration of oxytocin augmentation and total oxytocin dosage with PPH risk. Wide confidence intervals were seen for the dose-response curve, while changes in EBL with oxytocin duration or dosage were minor. These findings were consistent among women with spontaneous labor onset and vaginal delivery.
A standardized mean difference of under 0.2 was found for all covariates after weighting. No model identified a significant association between oxytocin use and PPH nor EBL.
These results indicated a gradual increase of PPH and EBL risks with oxytocin duration and dosage. However, associations with oxytocin for augmentation are not clinically significant when compared to women with similar obstetrical characteristics.
Reference
Zhu H, Lu D, Branch DW, et al. Oxytocin is not associated with postpartum hemorrhage in labor augmentation in a retrospective cohort study in the United States. Am J Obstet Gynecol. 2024;230:247.e1-9. doi:10.1016/j.ajog.2023.07.054
