This study evaluated in vitro immune responses to Escherichia coli lipopolysaccharide in maternal and fetal blood. Samples were concurrently obtained from maternal venipuncture and umbilical cord blood samples and cultured with the E. coli endotoxin, and cytokines were assayed. There were statistically significant correlations between maternal and fetal samples. This demonstrates maternal and fetal immune communication and mutual programming during pregnancy. Subclinical infection, which predisposes to premature labor, could be detectable from a maternal blood sample even if derived only from the fetal compartment. A maternal blood panel test might serve as a diagnostic screen for subclinical infection in patients at risk for preterm labor.