In the previous report [Hain, 1940], with a view to examining hormone changes associated with the birth mechanism, the author investigated the output of pregnanediol and of the two combined oestrogens in women approaching parturition and also in one woman throughout the whole of a normal pregnancy. The larger series comprised both normal and toxaemic patients, none of whom received therapy; in no instance was the amount of free oestrogen excreted estimated. The present series investigates the problem of pregnancy and parturition from a different angle, in that it seeks to ascertain the hormone output associated with abortion. The series consists of women with histories of previous miscarriage or showing signs of threatened abortion in the pregnancy investigated, and falls into two parts: the first consisting of five women in whom both the oestrogen and the pregnanediol outputs were ascertained at very frequent intervals, and the second of over 100