Prepartum Milk Secretion (Without Removal) Results in the Formation of Colostrum

The milk formed before parturition is called colostrum. Its formation represents a secretory process in which lactogenesis occurs in the absence of milk removal. Lactation cannot fully blossom until pregnancy is terminated, however, because of the inhibitory effects of progesterone and estrogen on milk secretion, inhibitory factors that are removed at or just before delivery.