There are a few different factors that affect uterus size, in both a healthy and an unhealthy uterus. A healthy uterus will vary in size monthly, due to the menstrual cycle. Age and pregnancy are also normal factors that change the size of a uterus. Some disease, such as fibroids and endometriosis can also enlarge the uterus.
One of the most common factors that affect the size of the uterus is the menstrual cycle. Most women ovulate every month, which means the uterus is preparing for conception. This process causes the endometrium, or the wall of the uterus, to fill with blood and endometrial tissue. Naturally, as the uterine wall expands to fill with blood, the overall size of the uterus is enlarged. If conception does not occur, then the uterus will shed the extra blood during menstruation, and more than likely, the whole process will reoccur the following month.
Another factor that affects healthy uterus size is pregnancy. When conception occurs successfully, the uterus will expand as the fetus grows within it. This is a perfectly healthy and normal function of the uterus. The uterus will be considerably smaller during the second month of pregnancy than it is during the eighth month. Whether or not pregnancy has occurred, and the development of the fetus both affect the size of the uterus.
Age is also a factor that affects uterus size. Children have small bodies, and therefore, smaller organs, including the uterus, than adults. The uterus also shrinks in post-menopausal women. It shrinks back to about the size of that of a pre-adolescent girl. The organ is no longer active, so it is spared vital resources that the remaining active organs can use.
Uterus size is also affected by the presence of uterine fibroids, also called leiomyoma, or just myoma. Fibroids are tumors that grow inside the wall of the uterus. These tumors are almost never cancerous, and are typically small. They can grow up the size of grapefruits, and in these cases, they significantly affect the size of the uterus. Often when doctors diagnosis fibroids, they will compare the size of the uterus to stages of pregnancy.
Endometriosis is another disorder that can change the uterus size. Also called adenomyosis, endometriosis is a noncancerous disease that affects the endometrium, typically the back wall, or posterior side, of the uterus. This disease occurs when the endometrial tissue spreads and penetrates the muscle of the uterus. The uterus becomes hard and can reach up to twice its normal size. Endometriosis is most common in women who have already had children, but if left untreated, it can cause infertility.