The effect of fetal acidemia on fetal-placental vascular tone and production of the inflammatory cytokines interleukin-6 and tumor necrosis factor-α

Objective: Our purpose was to determine the effects of fetal acidemia on placental vascular tone and production of interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α). Study Design: With use of an ex vivo placental perfusion model, the maternal and fetal circulation of two cotyledons from five human placentas were perfused for 4 hours. The fetal circulation of one cotyledon was perfused with acidemic (pH 6.90) Hanksʹ balanced salt solution (HBSS), whereas the fetal circulation of the other cotyledon was perfused with physiologic (pH 7.35) HBSS. Fetal venous effluents were collected hourly, and IL-6 and TNF-α concentrations were determined by enzyme-linked immunosorbent assay. Cotyledon perfusion pressures were recorded every 10 minutes. Paired t tests were used to compare differences in cytokine production and perfusion pressure between the cotyledons. Results: Fetal-placental vascular perfusion pressure was consistently reduced from baseline under acidemic, but not physiologic, conditions with statistical significance achieved from 20 minutes onward (P< .05). IL-6 and TNF-α increased exponentially over time for both conditions (P< .05). There was no difference in cytokine production when acidemic conditions were compared with physiologic conditions (P< .05). Conclusion: Fetal-placental vasodilation may be a compensatory mechanism to improve acidemic conditions. Unlike fetal hypoperfusion or fetal hyperoxia, fetal acidemia does not result in elevated placental cytokine levels. ( Am J Obstet Gynecol 2002;187:894-7.)