The Effectiveness of Mineral Oil in Preventing Obstetric Lacerations Among Nulliparous Women During the Second Stage of Labor: A Retrospective Study.

OBJECTIVE: Perineal trauma, particularly obstetric anal sphincter injuries (OASIS), results in significant maternal morbidity, including increased blood loss, perineal pain, sexual dysfunction, and bowel and/or bladder dysfunction. The use of oil on the perineum in the second stage of labor has not been well studied. We aimed to evaluate the effect of mineral oil on reducing perineal laceration incidence and severity. METHODS: We conducted a retrospective cohort study of nulliparous patients undergoing vaginal delivery between January 1, 2018, and December 31, 2020, at an academic medical center. Administration of mineral oil to the perineum during the second stage of labor was identified through pharmacy logs. The primary outcome was the rate of genital tract laceration. Univariate analyses and multivariate regression were performed using Stata Standard Edition. RESULTS: Of 1,171 patients, 250 (21.3%) received mineral oil. When controlling for episiotomy, patients who received mineral oil had similar rates to those who did not receive oil of any genital tract laceration (92.5% vs. 89.9%, p =.261), any anterior laceration (26.9% vs. 29.6%, p =.449), and any posterior laceration (86.3% vs. 81.1%, p =.076). Patients who received mineral oil had significantly higher rates of OASIS (11.3% vs. 6.7%, p =.024). CONCLUSION: The use of mineral oil in the second stage of labor does not reduce genital tract laceration incidence or severity. This study demonstrates the need to utilize evidence-based obstetric guidelines and continue investigating strategies to reduce severe genital tract injury.