Serum oestrogens and progesterone in mother and infant at delivery.

Whereas maternal venous levels of progesterone and oestrogens have been studied intensively in relation to parturition, little attention has been directed to fetal levels. In this study progesterone, oestrone (E1), oestriol (E2) and oestriol (E3) were measured in umbilical artery (UA) and umbilical vein (UV) serum at vaginal delivery (after induced or spontaneous onset of labour) and at elective Caesarean section. At least 14 samples were included in each group. All UV serum steroid levels were consistently higher than UA serum steroid levels. Cord serum levels of progesterone and arterio-venous differences were higher at vaginal delivery than at Caesarean section although maternal levels changed little. E1 and E2 levels were similar after spontaneous labour and at Caesarean section but were higher (P less than 0-05) after induced labour although E3 levels did not alter. E1 and E2 were higher and progesterone lower in primiparae than in multiparae. Fetal sex made no differences. These results suggest that induction of labour with oxytocin results in altered fetal hormone levels, that maternal hormone levels provide a poor reflection of fetal changes,and that current views about the mechanism of the onset of labour in animals may not be appropriate for man.