Amniotic Fluid Eicosanoids in Preterm and Term Births: Effects of Risk Factors for Spontaneous Preterm Labor

OBJECTIVE: To evaluate amniotic fluid arachidonic acid metabolites using enzymatic and nonenzymatic (lipid peroxidation) pathways in spontaneous preterm birth and term births, and to estimate whether prostanoid concentrations correlate with risk factors (race, cigarette smoking, and microbial invasion of amniotic cavity) associated with preterm birth. METHODS: In a case-control study, amniotic fluid was collected at the time of labor or during cesarean delivery. Amniotic fluid samples were subjected to gas chromatography, negative ion chemical ionization, and mass spectrometry for prostaglandin (PG) E(2), PGF(2 alpha), and PGD(2) and for 6-keto-PGF1 alpha (thromboxane 2 and F2-isoprostane). Primary analysis examined differences between prostanoid concentrations in preterm birth (n=133) compared with term births (n=189). Secondary stratified analyses (by race, cigarette smoking, and microbial invasion of amniotic cavity) compared eicosanoid concentrations in three epidemiological risk factors. RESULTS: Amniotic fluid F2-isoprostane, PGE(2), and PGD(2) were significantly higher at term than in preterm birth, whereas PGF(2 alpha) was higher in preterm birth 6-keto-PGF1 alpha and thromboxane 2 concentrations were not different. Data stratified by race (African American or white) showed no significant disparity among prostanoid concentrations. Regardless of gestational age status, F2-isoprostane was threefold higher in smokers, and other eicosanoids were also higher in smokers compared with nonsmokers. Preterm birth with microbial invasion of amniotic cavity had significantly higher F2-isoprostane compared with preterm birth without microbial invasion of amniotic cavity. CONCLUSION: Most amniotic fluid eicosanoid concentrations (F2-isoprostane, PGE(2), and PGD(2)), are higher at term than in preterm births. The only amniotic fluid eicosanoid that is not higher at term is PGF(2 alpha). (Obstet Gynecol 2011;118:121-34) DOI: 10.1097/AOG.0b013e3182204eaa