* Endocrine transition from progesterone to oestrogen dominance under the influence of gonadotrophins LH and FSH.
* Endocrine transition from progesterone to oestrogen dominance under the influence of gonadotrophins LH and FSH.
−
* Follicular growth and regression of the corpus luteum of the previous cycle (in polyoestrous species).
+
* Follicular growth and [[Female_Reproductive_Tract_-The_Ovary_-_Anatomy_%26_Physiology#Corpus_Luteum_Regression|regression of the corpus luteum]] of the previous cycle (in polyoestrous species).
* Uterus enlarges slightly
* Uterus enlarges slightly
* Endometrium becomes congested and oedematous, glands show secretory activity.
* Endometrium becomes congested and oedematous, glands show secretory activity.