what is an endometrium and how does it change during pregnancy ?

Endometrium – The endometrium is the uterine lining or inner membrane of the womb or uterus. Normally this lining is shed every month due  to hormone changes that accompany a normal menstrual period. The endometrium grows back slowly until the next month when the cycle repeats  itself. That is unless you are pregnant… During pregnancy, the endometrium glands and blood vessels increase in number and size and due to changing hormones and absense of a menstrual period the endometrium is not shed or lost. The lining becomes the foundation for the placenta, which supplies oxygen and nutrition to the embryo and fetus.