Abstract
To study changes of circulating hormone levels related to parturition, oxytocin, estrogen stimulated neurophysin (ESN), and steroids derived from the feto-placento-maternal unit were measured serially in 30 pregnant women a week before the onset of labor, during first and second stages of labor, at delivery, and two hours after delivery. No apparent changes in the levels of estrone, estradiol or estriol were observed before or during labor, but they decreased dramatically two hours after delivery. Progesterone decreased significantly after the onset of labor from the levels measured a week before delivery, whereas DHA and DHA-S increased and peaked at delivery. Oxytocin concentration started to increase after the onset of labor and reached a maximum at delivery. ESN levels, however, did not change significantly in the period studied. There was positive correlation between the levels of estrone and ESN, estradiol and ESN, DHA-S and oxytocin, and, ESN and oxytocin. From the results obtained above, it was evident that the levels of both estradiol and estrone correlated well with that of ESN. The results also suggested that the initiation of labor may be closely related to changes of steroids levels, including decrease of progesterone and increment of DHA-S. Oxytocin may also be involved in the promotion of labor.
