Differences in the fetal interleukin-6 response to microbial invasion of the amniotic cavity between term and preterm gestation

Abstract

Background/objective: Fetal inflammatory response has been implicated as a mechanism of multi-system organ injury in preterm and term neonates. Microbial invasion of the amniotic cavity (MIAC) isfrequently associated with a fetal inflammatory response. However, there are no studies comparing the fetal response to MIAC in term and preterm gestations. The purpose of this study was to compare theumbilical cord plasma interleukin-6 (IL-6) concentrations in term and preterm neonates in the presence or absence of MIAC.Study design: Umbilical cord blood was obtained at birth from 252 neonateswhose mothers had an amniocentesis within 48 h of delivery (preterm delivery, n = 62; term delivery, n = 190). MIAC was defined as a positive amniotic fluid culture for bacteria or genital mycoplasmas.IL-6 was measured by a sensitive and specific immunoassay.Results: The median IL-6 concentration in umbilical cord plasma was significantly higher in preterm neonates than in term neonates (median13.4 pg/ml, range 0.1-676 pg/ml vs. median 3.2 pg/ml, range 0.1-408 pg/ml; p < 0.0001). In the context of MIAC, the median umbilical cord plasma IL-6 concentration was significantly higher inpreterm than in term neonates (median 31.6 pg/ml, range 1.4-676 pg/ml vs. median 11.7 pg/ml, range 1.3-82 pg/ml, respectively; p < 0.05). Neonates born to mothers with a positive amniotic fluidculture had a significantly higher median IL-6 concentration than neonates born to mothers with a negative amniotic fluid culture (preterm: median 31.6, range 1.4-676 pg/ml vs. median 8.0, range 0.1-656pg/ml; p < 0.05 and term: median 11.7, range 1.3-82 pg/ml vs. median 3.1, range 0.1-408 pg/ml; p < 0.01, respectively).Conclusions: The preterm fetus is capable of mountinga systemic cytokine response as measured by IL-6 in its peripheral blood. In the setting of MIAC, a fetal IL-6 response is higher in preterm than in term gestation.