Distance between the pubic bone and uterine fundus (top of the uterus). The fundal height is used to estimate uterine size and fetal age. This is a rough estimate of the size of the fetus and is used to screen for problems with fetal growth. This basic measurement is obtained at most prenatal visits. The fundal height (in centimeters) is taken with a tape measure from the top of the pubic bone to the top (fundus) of the uterus. The fundal height increases as the uterus enlarges. Between 18 and 30 weeks of gestation the fundal height in centimeters is roughly the same as the number of weeks of gestation.