SUMMARYThe excretion of preganediola and the 6‐oxygenated metabolites of progesterone was measured during the last 12 weeks of pregnancy in fifty‐five women. There was no significant change in pregnanediol excretion during the last 10 weeks of pregnancy but during this time there was a significant increase in the excretion of the 6‐oxygenated metabolites. There was a significant correlation between the excretion of these latter metabolites and both fetal and placental weights at term. It is suggested that the 6‐oxygenated metabolites may be arising from the fetal 6‐hydroxylation of progesterone. In some patients with severe toxaemia pregnanediol excretion was low although excretion of 6‐oxygenated metabolites was within the n