Inorganic phosphorus and zinc concentrations in amniotic fluid: correlation with intra-amniotic infection and bacterial inhibitory activity.

Concentrations of zinc and inorganic phosphorus were determined in amniotic fluid from 41 patients with intra-amniotic infection and from 40 uninfected, control patients. Also determined was amniotic fluid inhibitory activity to an Escherichia coli test organism. Compared to amniotic fluid from control patients, that from patients with intra-amniotic infection had significantly higher mean concentrations of phosphorus. In specimens free of meconium, the mean concentrations of phosphorus were still significantly higher. Assays for inhibitory activity were performed with 62 samples of fluid (25 noninhibitory, 37 inhibitory). Although noninhibitory fluid had higher mean concentrations of phosphorus and zinc, these differences did not hold after meconium-stained samples were excluded. No correlation was found between phosphorus-to-zinc ratio and either intra-amniotic infection or inhibitory activity. However, there are important differences in population and techniques between this and related studies.