Higher risk of adverse outcomes linked to low OVD volume in hospitals

Higher risk of adverse outcomes linked to low OVD volume in hospitals | Image Credit: © Louis-Photo - © Louis-Photo - stock.adobe.com.

Adverse perinatal outcomes are more common from operative vaginal deliveries (OVDs) in hospitals with low OVD volume, according to a recent study published in JAMA Network Open.¹

The mode of delivery is a key factor of obstetric and birth outcomes. OVD is a method of delivery facilitated by forceps or vacuum devices when clinically indicated. It is often used for protracted second stage of labor, fetal compromise, and medical conditions in the birthing parent.

Cesarean delivery should be avoided when possible to reduce risks of longer hospital stay, more difficult recovery, and complications. The rate of OVD in the United States has remained stable since 2014, with a rate of 3.04% reported in 2020.² This is a significant reduction compared to the 1994 rate of 9.4%.¹

Currently, the reasons behind the decrease in OVD rates remain unclear. However, low-volume settings have historically been linked to increased odds of adverse health outcomes.

To evaluate the association between hospital-specific OVD volume and resultant perinatal outcomes, investigators conducted a retrospective, population-based, cohort study. Discharge data from California between 2008 and 2024 was used for the analysis.

Vital statistics data from the California Department of Public Health was linked to public discharge data from the Department of Health Care Access and Information. Diagnosis and procedure codes were based on the International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) and ICD-10-CM.

Participants included patients with a singleton, nonanomalous, full-term OVD. Those with multifetal gestation, anomalous birth, non-vertex presentation, and gestational age under 37 weeks or over 42 weeks were excluded from the analysis.

Hospitals were categorized into tertiles based on OVD rates, which were calculated as the proportion of OVDs at a hospital during the study period compared to all deliveries. OVD volume under 5.2% was considered low, 5.2% to 7.4% medium, and 7.4% or greater high.

Demographic data collected included age, race and ethnicity, education, parity, insurance, prepregnancy body mass index, birth weight, and gestational age. ICD-9-CM and ICD-10-CM codes were used to identify adverse outcomes in birthing parents and infants.

There were 306,818 participants aged a mean 28.5 years included in the final analysis, 50.6% of whom had public insurance. A low OVD volume hospital was the setting for 19.9% of OVDs, medium volume for 31.5%, and high volume for 48.5%.

Patients giving birth in hospitals with a low OVD volume were more often Hispanic, aged under 20 years, and with obesity. The risk of obstetric anal sphincter injuries was increased in this setting, at 12.16% vs 11.07% in medium volume hospitals and 9.45% in high volume hospitals.

Cervical lacerations rates were also increased, at 0.31%, 0.25%, and 0.23%, respectively. Additionally, postpartum hemorrhage rates were 5.43%, 4.20%, and 3.75%, respectively.

Adjusted relative risks (aRRs) for obstetric anal sphincter injuries and postpartum hemorrhage were both 1.36 for low volume hospitals vs high volume hospitals. However, the aRR for cervical lacerations was not statistically significant at 1.30.

For neonatal outcomes, rates of shoulder dystocia, neonatal intensive care unit (NICU) admission, subgaleal hemorrhage, facial nerve injury, fractures, and brachial plexus injury were increased in low volume hospitals vs medium and high volume hospitals. For shoulder dystocia, rates were 3.84%, 3.50%, and 2.80%, respectively.

Rates for NICU admission were 10.09%, 9.33%, and 8.73%, respectively, vs 0.27%, 0.18%, and 0.10%, respectively, for subgaleal hemorrhage. Additional rates included 0.05%, 0.03%, and 0.03%, respectively for facial nerve injury, 0.53%, 0.49%, and 0.37%, respectively, for fractures, and 0.41% 0.30%, and 0.20%, respectively, for brachial plexus injury.

These results indicated an association between hospital OVD volume with maternal and infant outcomes. Investigators recommended further research to determine the causes of this association and how these causes may be mitigated.

References

1. Willy AS, Hersh AR, Garg B, Caughey AB. Obstetric outcomes by hospital volume of operative vaginal delivery. JAMA Netw Open. 2025;8(1):e2453292. doi:10.1001/jamanetworkopen.2024.53292
2. Osterman MJK, Hamilton BE, Martin JA, Driscoll AK, Valenzuela CP. Births: final data for 2020. Centers for Disease Control and Prevention. February 7, 2022. Accessed January 8, 2024. https://stacks.cdc.gov/view/cdc/112078