The Prevalence of Perineal Tears Among Women Having Spontaneous Vaginal Births with Intrapartum Fever

Perineal tears are common during vaginal delivery and are associated with significant maternal morbidity. While chorioamnionitis and intrapartum fever are known to affect labor dynamics and perineal tissue integrity, their relationship with perineal trauma in spontaneous vaginal deliveries has not been established. This study aimed to evaluate the prevalence of perineal tears among women with intrapartum fever who delivered spontaneously. This retrospective cohort study included women who underwent spontaneous vaginal delivery during 2013-2021 in Israel. The study group comprised women diagnosed with intrapartum fever (≥38 °C), while afebrile women served as controls in a 1:2 ratio matched by age (<35 or ≥35 years) and gestational age (preterm/term). Perineal tears were classified according to the Royal College of Obstetricians and Gynaecologists (RCOG) criteria. Multivariable logistic regression was performed to adjust for statistically significant variables including obesity, induction of labor, epidural analgesia, amniotomy, delivery week, gestational diabetes, birth number, duration of the second stage of labor, and episiotomy. The cohort included 373 women with intrapartum fever and 746 controls. The overall rate of perineal tears was similar between febrile and afebrile women (42% vs. 40%; adjusted odds ratio [aOR] 0.99, 95% confidence interval [CI] 0.72-1.36). However, the rate of obstetric anal sphincter injury (OASIS) was lower among women with intrapartum fever (0.5% vs. 2.0%; aOR 0.10, 95% CI 0.02-0.52). Intrapartum fever was associated with higher rates of postpartum hemorrhage, manual exploration of the uterus, endometritis, anemia, and blood transfusion. Bacterial cultures were positive in 31% of febrile women, predominantly Escherichia coli and Group B Streptococcus, without association with perineal trauma. Alltogether, Intrapartum fever did not increase the risk of perineal tears in spontaneous vaginal deliveries and was paradoxically associated with a lower rate of OASIS. Further studies are warranted to explore the underlying physiological mechanisms linking temperature and perineal tissue resilience.