Carbone et al. postulated the following two main hypotheses regarding the association between PTD and cfDNA concentration: (1) a higher cfDNA value could be related to the breakdown of the placental barrier in line with labour onset and/or with preliminary events that precede labour; however, this mechanism appears to be more related to labour itself and not PTD; (2) cffDNA being non-self DNA could play a pro-inflammatory role that activates several factors, including the Toll-like receptor (TLR) 9 pathway and stimulator of interferon genes (STING) pathway. Here, STING1 is linked to Bjornstad syndrome.