the present invention relates to methods and kits useful for predicting the time of onset of labour in a pregnant subject . in particular , the invention relates to methods and kits for predicting the time of onset of labour wherein the levels of at least two hormones , selected from estriol , estradiol and progesterone , are determined and a ratio of said levels is calculated , and wherein the time of onset of labour is predicted by comparison of said ratio with a predetermined ratio . the invention further contemplates methods for preventing preterm delivery of an infant / offspring .