Lactate levels increase significantly in the second stage of spontaneous and induced labor

Abstract

Lactate is frequently observed as a component of sepsis bundles, however, there is a paucity of data for normal ranges in labor. Because of this, our aim was to survey maternal lactate levels in uncomplicated labor. This was a prospective convenience sampling of patients at term presenting with spontaneous labor and for induction at a single academic center. Blood was collected at admission, complete cervical dilation, and every 30 minutes during the second stage of labor for up to 3 hours or until delivery. Samples were processed and transported on ice to an on-site laboratory within 30 minutes for analysis of plasma lactate using enzymatic oxidation and colorimetric assay (Roche Lactate Gen.2). The primary outcome was change in lactate level over time during the second stage of labor. Statistical analysis included a mixed effects repeated measures model, with chorioamnionitis as a fixed effect and time as a random effect with p < 0.05 considered significant. From January 7, 2021, through December 30, 2021, 38 patients were enrolled. Eight patients withdrew after the baseline level was drawn. Lactate was obtained for 23 patients at complete dilation, and for 14 patients during maternal pushing. Beginning at the second stage, mean lactate was 2.76 mmol/L (95% CI 2.01, 3.51). Lactate significantly increased with time (p < 0.001) with mean change in lactate level 1.9 mmol/L over 30 minutes of observation (Figure 1a). Lactate level was increased in patients with chorioamnionitis compared to uninfected laboring patients, but this difference was not statistically significant (p = 0.67) (Figure 1b). Lactate increases significantly in the second stage of uncomplicated spontaneous or induced labor from a baseline considered outside the normal range in nonpregnant individuals. Obstetricians should use caution in interpreting abnormal lactate levels in otherwise uncomplicated laboring patients with or without chorioamnionitis.