OBJECTIVE: To test the effect of ampicillin on amnioticinterleukin- 6 (TL- 6) and prostaglandin E2 (PGE2) release. METHODS: In an in vitro study, IL- 6 and PGE2 release from amnion- like Wistar Institute Susan Hayflick cells was assayed under basal conditions, as well as after incubation with ampicillin. In an in vivo study, amniotic fluid IL- 6 was assayed in a total of 212 patients submitted to genetic amniocentesis during the 17th week of their singleton physiological pregnancy. The study population was subdivided as follows: 92 patients sampled before ampicillin administration, 70 patients sampled 4 hours after administration of 1 g ampicillin, and 50 patients sampled 12 hours after administration of 1 g ampicillin. RESULTS: At doses ranging from 10- 7 to 10- 4 M, ampicillin decreased IL- 6 release from Wistar Institute Susan Hayflick cells. The drug effect was already statistically significant (- 30% ; P < .05)- at the lowest concentration tested (10- 7 M), reaching the maximum (- 50% ) at 10- 6 M after 4 hours of incubation. Moreover, ampicillin concentrations ranging from 10 - 7 to 10- 4 M decreased PGE2 release from Wistar Institute Susan Hayflick cells; maximal inhibition was reached at 10 - 6 M after 4 hours (- 40% ; P < .05). Finally, IL- 6 levels measured in amniotic fluid of patients sampled 4 hours after ampicillin administration proved strongly and significantly reduced when compared with those sampled either before or 12 hours after treatment (P < .001). CONCLUSION: The capacity of ampicillin to directly decrease amniotic IL- 6 and PGE2 release should be considered in the management of bacterial and nonbacterial inflammatory complications of pregnancy mediated by the cytokine and prostanoid interaction. OBJECTIVE: To test the effect of ampicillin on amnioticinterleukin-6 (TL-6) and prostaglandin E2 (PGE2) release. METHODS: In an in vitro study, IL- 6 and PGE2 release from amnion- like Wistar Institute Susan Hayflick cells was assayed under basal conditions, as well as after incubation with ampicillin. In an in vivo study, amniotic fluid IL-6 was assayed in a total of 212 patients submitted to genetic amniocentesis during the 17th week of their singleton physiological pregnancy. The study population was subdivided 70 patients sampled 4 hours after administration of 1 g ampicillin, and 50 patients sampled 12 hours after administration of 1 g ampicillin. RESULTS: At doses ranging from 10-7 to 10-4 M, ampicillin decreased IL-6 release from Wistar Institute Susan Hayflick cells. The drug effect was already statistically significant (- 30%; P <.05) - at the bottom concentration tested (10-7 M), reaching the maximum ( - 50%) at 10-6 M after 4 hours of incubation. Moreover, ampicillin concentration ranging from 10-7 to 10-4 M decreased PGE2 release from Wistar Institute Susan Hayflick cells; maximal inhibition was reached at 10-6 M after 4 Finally, IL-6 levels measured in amniotic fluid of patients sampled 4 hours after ampicillin administration were strongly and significantly reduced when compared with those sampled either before or 12 hours after treatment (P < .001). CONCLUSION: The capacity of ampicillin to directly decrease amniotic IL-6 and PGE2 release should be considered in the management of bacterial and nonbacterial inflammatory complications of pregnancy mediated by the cytokine and prostanoid interaction.