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FETAL PLASMA STEROIDS IN RELATION TO PARTURITION III. THE EFFECT OF PARITY AND METHOD OF DELIVERY UPON UMBILICAL PLASMA OESTRONE AND OESTRADIOL LEVELS

Unconjugated oestrone and oestradiol levels were measured in human umbilical venous plasma at delivery after 38 to 40 weeks' gestation. A significant effect of parity (P<0.05) upon oestrogen levels was observed following spontaneous vaginal delivery. In eight primiparous patients the mean (±S.E.) oestrone and oestradiol levels were 25.0 ± 5.3 ng./ml. and 6.6 ± l.2 ng./ml. respectively whilst in eight multiparous patients they were 10.4 ± 3.4 ng./ml. and 3.6 ± l.0 ng./ml. respectively. The two groups showed no significant difference in the duration of labour. No effect of parity upon oestrogen levels was observed following elective Caesarean section or emergency Caesarean section when the patients were in early labour. The mean ratio for oestrone to oestradiol levels in umbilical venous plasma following spontaneous delivery (3.3 to 3.7: 1) was significantly higher (P<0.01) than the mean ratio in patients delivered by Caesarean section (0.6 to 1.1: 1). It is concluded that in spontaneous vaginal delivery at term the changes in placental metabolism associated with established labour are typified by an alteration in oestrone to oestradiol ratios with an elevation of the oestrone levels in umbilical venous plasma. The highest umbilical venous oestrone levels were found in primiparous patients after spontaneous vaginal delivery and this may reflect on increased metabolic activity associated with labour in those patients.