Fetal Responses to Maternal and Intra-Amniotic Lipopolysaccharide Administration in Sheep

A link between intrauterine infection and premature labor is widely accepted, yet the fetal inflammatory responses to such infections are not well understood. Our aim was to use a sheep model in which an inflammatory state was induced by lipopolysaccharide (LPS) administration during pregnancy to the maternal systemic, intra-amniotic or extra-amniotic compartments. Fetal and maternal blood gases and uterine electromyographic activity along with fetal and maternal circulating concentrations of prostaglandins PGE2 and PGFM, cortisol, and interleukin-6 were determined. Maternal systemic LPS treatment resulted in mild maternal hypoxemia, a rise in temperature, greater fetal hypoxemia, and a marked rise in fetal cortisol and PGE2 concentrations that persisted for 48 h. Intra-amniotic administration of LPS at doses higher than those used systemically caused an increase in fetal cortisol and PGE2 concentrations as well as a rise in uterine activity, but these were lesser in magnitude. Extra-amniotic LPS administration caused no overt fetal or maternal inflammatory responses. We conclude that maternal LPS treatment markedly elevated fetal cortisol and PGE2 concentrations. This may be a potential protective mechanism that aids the fetus in the event of premature delivery. The attenuated fetal response to intra-amniotic LPS treatment, despite the much higher dose used, may support a role for the amniotic fluid in protecting the fetus from endotoxin exposure during pregnancy.