The fundus is the round portion of the uterus found at the top. It is found higher on the uterus than the entrance of the fallopian tubes on the uterus. It is formally known as the fundus uteri.
The fundus is the topmost portion of the uterus and is known as the roof of the uterine cavity. During pregnancy, this is usually when the fertilized egg implants. The fundus and uterus can stretch significantly throughout pregnancy without any trauma or damage.
Throughout pregnancy the uterus grows to make room for the growing fetus. Doctors check the fundal height, or the top of the fundus, through gentle pressure on the abdomen to ensure that the pregnancy is progressing correctly. The fundal height in centimeters should be equivalent to the number of weeks of the pregnancy that have been completed. If the fundal height is too large or too small based of the number of weeks into the pregnancy, it can be an indication of a growth issue that requires further testing.
During labor, the fundus helps to expel the fetus from the mother's body through a series of tightening contractions. The fundus produces very strong contractions that help propel the fetus forward into the birth canal.