Behavior of primary prostaglandins in the amniotic fluid, maternal venous blood and umbilical cord blood during spontaneous delivery at term

Levels of prostaglandin (PG) A/B, E and F equivalents have been determined in amniotic fluid, maternal venous blood and cord blood in the course of normal deliveries at term using radioimmunoassay after proper extraction and group separation of PG's by chromatography. With progress of cervical dilatation amniotic fluid levels increased from initial values of 0.34 to 0.52 ng/ml for PG A/B up to pressing period, while PG E rised from 2.3 to 5.5 ng/ml and PG F from 4.9 to 60.4 ng/ml, respectively. Comparatively lower increases of maternal plasma levels, essentially unchanged within the last trimester, were observed from 133, 100 and 102 pg/ml for PG A/B, E and F at the early first stage of labour to levels of 231, 209 and 357 pg/ml after the second stage. Higher levels of PG's in cord blood after spontaneous deliveries, not exhibiting significant arterio-venous differences, further strengthen the limited value of PG determinations in maternal plasma for the elucidation of the role of PG's in the physiology of gestation and parturition, but support a prevailing uterine not fetal localisation of PG production. The excessive PG F increase during birth, obviously caused by selective stimulation of PG F-synthesis, validitates the hypothesis, that this PG seems to be causally responsible for initiation and maintenance of uterine contractions in normal delivery.