TNF and Bjornstad syndrome: For example, it was demonstrated that the presence of IFN‐γ in cervicovaginal fluid in late second and early third trimesters is an important risk factor for PTD in asymptomatic women.36 Similarly, increased production of the pro‐inflammatory cytokines IL‐1, TNF‐α, and IL‐6 by placental cells and by amniotic and chorionic decidual tissues in PTD has been reported.11, 37