Objectives: To assess whether there is an association between high lactate concentration in amniotic fluid (AF) and labor dystocia.
Design: Prospective observational study.
Setting: Labor ward at General South Hospital, Stockholm, Sweden.
Population and methods: Women in active labor attending labor ward, having at least two consecutive measurements of lactate concentration in AF, measured 60 minutes apart.
Main outcome measure: Dysfunctional labor, defined as instrumental or operative delivery due to dystocia.
Results: Among women with spontaneous vaginal deliveries (n=23) the mean lactate concentration in AF during labor was 8.9 mmol/l (range 6.6-10.8), and among women with operative delivery due to labor dystocia (n=31) the corresponding value was 10.9 mmol/l (range 8.0-16.1) (p<0.001). Of 29 women with a high lactate concentration (> or =10.1 mmol/l) in at least two consecutive measures collected at least 60 minutes apart, 25 (86%) were delivered instrumentally/operatively due to dystocia. Using this definition of a positive test, the diagnostic accuracy to predict operative delivery due to dystocia was: sensitivity 81% (25/31), specificity 83% (19/23), positive predictive value 86% (25/29), and negative predictive value 76% (19/25). The likelihood ratio was 5.0 for a positive test and 0.2 for a negative test.
Conclusions: High lactate concentration (> or =10.1mmol/l) in at least two consecutive samples of AF collected during labor 60 minutes apart is strongly associated with dystocia. This method might be useful in clinical management to identify labor dystocia at an early stage of labor.