1. Women with amniotic fluid lactate levels ≥10mmol/L were more likely to experience abnormal labor and Caesarean delivery.
2. Amniotic fluid lactate levels ≥10mmol/L were associated with fetal intolerance and uterine tachysystole.
Evidence Rating Level: 1 (Excellent)
Study Rundown: Dystocia is a term used to describe labor patterns that deviate from normal and includes protraction disorders, defined as slower than expected progress, and arrest disorders, defined as complete cessation of progress. Risk factors are related to the uterus, fetus, and shape or size of the maternal pelvis. Depending on the stage and phase of labor and fetal heart rate patterns, management of labor dystocia may include augmentation with oxytocin or amniotomy or decision to proceed with Cesarean delivery. As labor progresses, the myometrium can become fatigued and transition from aerobic to anaerobic metabolism, which generates an increase in intramuscular lactic acid levels. A prior study found an association between dystocia and amniotic fluid lactate (AFL) levels when rupture of membranes occurred. In the present work, the authors evaluated the relationship between labor disorders and CD and AFL levels at diagnosis and throughout the 1st stage of labor. They found that higher levels of AFL were associated with dystocia and CD. This finding suggests that AFL may be useful in evaluating risk for labor complications in nulliparous women with term pregnancies.
Strengths of the study included prospective design and large sample size. Inclusion of only nulliparous women with term pregnancies limited generalization to other populations at high risk for labor complications. Further evaluation of the predictive value of AFL and cost-effectiveness studies are needed to determine the utility of AFL as a clinical tool for widespread use.
Relevant Reading: Dysfunctional labor and myometrial lactic acidosis
In-Depth [prospective cohort]: This study evaluated the ability of amniotic fluid lactate to predict dystocia and CD in 905 nulliparous women in spontaneous labor with cephalic, term infants. Primary outcomes of interest were dystocia and Caesarean delivery. Secondary outcomes were maternal and fetal outcomes.
Compared to women with AFL levels of 0-4.9mmol/L, women with AFL levels ≥5mmol/L (OR 1.60, 95% CI 1.06-2.39) and ≥10mmol/L (OR 1.72, 95% CI 1.01-2.93) were more likely to experience dystocia. AFL ≥10mmol/L was an independent predictor of CD (OR 3.35, 95% CI 1.73-6.46). The negative predictive value of AFL ≥10mmol/L was 94% and positive predictive value was 18%. AFL ≥10mmol/L was associated with fetal intolerance and uterine over-contraction (p=0.005).
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