Similarly, IL-1β produced by polymorphonuclear leukocytes (Vrachnis et al., 2012), appears to be a major effector of infection-associated PTB (Genc et al., 2004; Sadowsky et al., 2006), with elevated levels identified in amniotic fluid of women diagnosed with amniotic infection (Romero et al., 1992a, Romero et al., 1992b; Romero et al., 2015). This evidence concerns the gene IL1B and infection.