Incidence of maternal tachycardia during the second stage of labor: a prospective observational cohort study

Objective: To our knowledge, this is the largest prospective study reporting on maternal heart rate (MHR) levels in laboring women (30 patients), and maternal tachycardia that is a potential risk factor in fetal monitoring confusion. Our objective was to analyze a large population of contiguous laboring patients and to assess the MHR levels attained during the second stage.

Methods: We performed a prospective study that analyzed MHR levels of second-stage laboring patients evaluating numerous predisposing maternal conditions. Univariate and stepwise multivariate logistic regression analysis were performed.

Results: A total of 1105 contiguous patients were analyzed and 33.9% had a sustained MHR ≥100; 18.8% had an MHR ≥110; and 9.1% had an MHR ≥120. Multivariate analysis of all potential predisposing maternal conditions did not reveal any specific variable as uniformly significant for predicting maternal tachycardia across all levels of analysis.

Conclusions: The incidence of maternal tachycardia in the second stage of labor is common. We recommend that if the MHR is ≥100 during labor, the simultaneous maternal and fetal heart rate (FHR) monitoring will be used to minimize the potential for fetal monitoring confusion and risking poor fetal outcome if the fetus is in distress.