This study seems to be the first report on the expression of CB during human pregnancy. This study found the link between the expression of CB receptors and PTB in analysed postpartum placentas. First of all, endocannabinoid receptors were present in the placental tissue after delivery. Moreover, PTB correlated with lower CB2 expression in the placentas and was significantly lower than in term births. This could result from a few mechanisms of CB action, namely its two main effects: influence on muscular tissue and engagement in the inflammatory process.