Plasma steroids in the foetal and maternal circulation at normal delivery and elective caesarean section

Maternal and foetal plasma collected at normal delivery and at elective caesarean section was assayed for sex steroid levels. Foetal cord plasma concentrations of progesterone, 17-hydroxyprogesterone, oestrone and oestriol were higher than maternal values at normal delivery, whereas oestradiol levels were lower. Oestrone concentrations were higher than oestradiol in the foetal circulation at normal delivery and oestrone values were higher following normal delivery than at elective caesarean section.