The uterus, a hollow muscular organ shaped like a flattened pear, is situated in the cavity of the true pelvis, behind the bladder and in front of the rectum. In it the fertilized ovum embeds, is nourished and protected for 40 weeks. SIZE OF THE UTERUS – The non-pregnant uterus weighs about 57G. and measures 7.6×5.1×2.5. The corpus or body is 5.1cm. long, the cervix 2.5cm. long. The walls of the uterus are 1.25cm. thick.