The uterus
A woman's uterus is also called her womb. When a woman is not pregnant her uterus is about the size of a clenched fist and pear-shaped. It lies behind her bladder and in front of her rectum or bowel. The uterus usually leans slightly forward so that it is almost resting on the bladder. For about 20% of women, their uterus leans backwards and is referred to as being
retroverted. This is a normal variation and does not generally affect conception, pregnancy, labour or the birth. The entrance or opening to the womb is called the cervix. This extends into the top of the vagina inside the woman's body.
Image 1-01 shows the uterus in relation to the female anatomy before pregnancy.
The uterus is made up of three layers:
The inner layer is the endometrium. This is the inside mucus lining of the uterus where the
placenta attaches.
The middle layer is made of different types of muscles, collectively called the myometrium. During pregnancy these muscle cells grow ten times in length and three times in width. Some of these muscles run lengthwise from the cervix, over the top of the uterus (also called the fundus) back down to the cervix on the other side. They contract and shorten during labour, pulling up the cervix and pushing your baby down the birth canal.
Other uterine muscles form thick bundles that criss-cross and intertwine, usually in the shape of a figure 8. The blood vessels from the mother to the placenta pass through the openings of the loops in these 8 shapes. After the birth, the uterus contracts these muscles around the blood vessels to naturally control bleeding.
The outer layer is the perimetrium. A fine outer layer separating the uterus from the intestines
Image 1-02 shows the mucus lining, inner muscle and outer layer of the uterus.
Image 1-03 shows the uterine muscles and how they criss-cross and intertwine during pregnancy.
Updated November 2007
Information sources