Changes

The concentration of progesterone increases after ovulation increasing the growth of glands found in the endometrium resulting in increased secretion. These secretions include mucin, carbohydrates and specific proteins that are designed for nourishment of the embryo prior to implantation. Progesterone also stimulates the growth of the endometrium and stabilises smooth muscle cells to ensure that they do not contract during foetal development. Once near term, the concentration of progesterone decreases, altering the ratio between progesterone and oestrogen. This stimulates myometrial activity and prepares the uterus for parturition.

The concentration of progesterone increases after ovulation increasing the growth of glands found in the endometrium resulting in increased secretion. These secretions include mucin, carbohydrates and specific proteins that are designed for nourishment of the embryo prior to implantation. Progesterone also stimulates the growth of the endometrium and stabilises smooth muscle cells to ensure that they do not contract during foetal development. Once near term, the concentration of progesterone decreases, altering the ratio between progesterone and oestrogen. This stimulates myometrial activity and prepares the uterus for parturition.

====Progesterone During Pregnancy====

====Progesterone During Pregnancy====

During pregnancy the plasma concentration of progesterone is maintained at an elevated level. Progesterone also inhibits secretion of GnRH and also prevents the [[Oestrous_Cycle_-_Anatomy_%26_Physiology#Oestrus|ovulation]] of follicles during the [[Oestrous_Cycle_-_Anatomy_%26_Physiology#Luteal_Phase|luteal phase]] and during pregnancy. The exception to this rule is the mare in which the progesterone concentration falls during the later stages of pregnancy.  

During pregnancy the plasma concentration of progesterone is maintained at an elevated level. Progesterone also inhibits secretion of FSH and LH (negative feedback at hypothalamic level  by  inhibiting GnRH) and thus also prevents the [[Oestrous_Cycle_-_Anatomy_%26_Physiology#Oestrus|ovulation]] of follicles during the [[Oestrous_Cycle_-_Anatomy_%26_Physiology#Luteal_Phase|luteal phase]] and during pregnancy. In most domestic species the corpus luteum  persists for the entire length of gestation.

<br />The exception to this rule is the mare in which the progesterone concentration falls during the later stages of pregnancy.  This is due to the regression of the corpus luteum around day 180 of the 330-340 day gestation period.

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