Placental leukotriene B4 release in early pregnancy and in term and preterm labour

The production of leukotriene B4 (LTB4) by the human placenta in vitro was measured by radioimmunoassay. In early pregnancy (7-12 weeks gestation) LTB4 production rate (pmol/mg dry weight/2 h) was 3.7 (2.6-4.7) (median and range; n = 9) and at term it was 0.7 (0.4-2.3; n = 10) in placental tissue obtained at elective caesarean section, and 2.7 (1.3-3.6; n = 10) in samples following labour of spontaneous onset and vaginal delivery. In spontaneous preterm labour (26-36 weeks gestation) with normal placental histology LTB4 production was 0.7 (0.3-1.7; n = 14), but it was significantly higher in preterm placentas with inflammatory infiltration: 3.1 (0.8-4.8; n = 6). These data show that the production of LTB4 by human placenta is high in early pregnancy, but remains low during the third trimester, with a significant increase in spontaneous labour at term. LTB4 output is low in uncomplicated preterm labour but markedly increased in chorioamnionitis-associated preterm labour.