Increasing number of cervical examinations in term labor does not increase the risk of maternal intrapartum fever.

INTRODUCTION

Intrapartum fever, a significant cause of maternal and neonatal morbidity, often arises from ascending infections into the uterus. Digital cervical examinations may facilitate the introduction of microorganisms, theoretically increasing fever risk. Prior studies on the association between exam frequency and fever have yielded inconsistent findings, a discrepancy that may be influenced by the choice of analytic method. We aimed to evaluate the dynamic relationship between cervical exam frequency and maternal fever risk using time-to-event analysis, modeling risk of fever as it evolves over the duration of labor.

METHODS

This retrospective cohort study included 3627 singleton pregnancies delivering at ≥37 weeks over a 6-year period. Patients were included if they reached the second stage of labor. Patients were categorized into three groups of number of cervical exams based on their natural distribution within the cohort to reflect clinical practice. Time-to-event analyses with Cox proportional hazard models were used to account for labor duration, adjusting for induction, Bishop score > 5, rupture of membranes (ROM), and interaction of ROM with time. A secondary analysis was performed by redefining time zero as the time of membrane rupture. Subgroup analyses included nulliparas and those admitted with less than 6 cm cervical dilation.

RESULTS

Among the 3627 patients, 160 (4.1%) developed intrapartum fever. In the unadjusted analysis, the risk of fever was higher in patients with more cervical exams: 1.5% in the 1-4 exam group, 4.1% in the 5-6 exam group, and 9.6% in the ≥7 exam group. However, after adjusting for confounding factors using time-to-event analysis, no increased risk of fever was observed with more exams. In fact, patients with ≥7 exams had the lowest risk (HR 0.24, 95% CI 0.13-0.43) compared to those with 1-4 exams. A similar association was demonstrated in subgroup analyses of nulliparous patients (p < 0.001) and those admitted with less than 6 cm cervical dilation.

CONCLUSION

In this time-to-event analysis, no association was found between an increased number of cervical examinations during labor and an elevated risk of maternal fever. The observed increased risk of intrapartum fever in prior studies using logistic regression may be influenced by confounding factors such as labor duration, rather than a direct causal relationship. These findings suggest that cervical exams, when clinically indicated, do not inherently increase the risk of fever.