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The association between lactate in vaginal fluid (‘LAC-test’) and time to spontaneous onset of labour in cases with suspected PPROM

      Objective

      In a previous study we have shown that measurement of lactate in vaginal fluid is a valid test for prelabour rupture of the membranes (PROM) and can predict onset of labour in women with suspected PROM. A lactate value >4.5 mmol/l was considered as a positive ‘LAC- test’.
      The aim of the present study was to analyze if quantitative measurement of lactate in vaginal fluid could predict onset of labour in women with suspected Preterm PROM (PROM= before 37 weeks gestation).

      Study design

      86 women attended the department of Obstetrics and Gynecology at Söder hospital in Stockholm between April 2002 and Mars 2004 with a history of suspected PPROM. A speculum examination was performed, and a sample of vaginal fluid was collected for lactate analysis. All women had singleton pregnancies and no history of uterine contractions. Seven patients were induced within 48 hours. The remaining 79 women constitute our material.

      Results

      The median lactate concentration was 1.9 mmol/l, and the median time between examination and onset of labour was 637.5 hours. (=26.6 days)
      Among those women with a positive ‘LAC-test’ median time between examination and onset of labour was 11.8 hours, while the corresponding value for those with a negative ‘LAC-test’ was 1272hours (=53 days) Among 23 women with lactate concentrations of >4.5 mmol/l 87% (n=20) had a spontaneous onset of labour within 48 hours. Within the group of 56 women with lactate concentrations of <4.5 mmol/l only 5% (n=3) started spontaneously within 48 hours.

      Conclusion

      The present study has shown that the ‘LAC-test’ is a good predictor for spontaneous onset of labour <48hours in women with suspected PPROM. We speculate that ‘LAC-test’ can be a vulnerable diagnostic test in the clinical management.