Abstract: The present invention relates generally to a method for estimating the time elapsed within a gestation period of a pregnant or potentially pregnant ruminant, such as a cow. The method involves estimating the time elapsed within a gestation period of a pregnant or potentially pregnant ruminant, including the steps of providing a sample from the ruminant; calculating a value of a pregnancy indicator in the sample; and applying a regression formula to the value of the pregnancy indicator to provide an estimate of the time elapsed within the gestation period. The method may further include the steps of categorising the pregnancy status of the ruminant, qualitatively assessing the level of the pregnancy indicator value for application thereto of the regression formula, using the time elapsed to derive an estimate of a gestation-related event, and validating the estimated date of a gestation related event.