Why is the ninth month called September?
endometrium en·do·me·tri·um (ěn'dō-mē'trē-əm)
n. pl. en·do·me·tri·a (-trē-ə)
The glandular mucous membrane comprising the inner layer of the uterine wall.
The mucous membrane that lines the uterus. A fertilized egg must embed itself in the endometrium in order to develop into an embryo. See more at menstrual cycle.