Fundal height is a medical term referring to the measurement of the approximate size of the uterus. It measures, in centimeters, the distance from the top of the uterus to the pubic bone. To measure fundal height, your doctor or nurse will probably use a tape measure to essentially measure the size of your baby bump. Here’s a look at the purpose of fundal height measurements, and what an abnormal measurement might mean.
Purpose of Fundal Height
Fundal height is used to assess fetal growth and development. Beginning in the second trimester, fundal height should generally match the number of weeks of your pregnancy. For example, if you were 26 weeks pregnant, your physician would expect your fundal height to measure approximately 26 centimeters. This correlation isn’t always exact and a variation on either side of a few centimeters isn’t usually any cause for concern. At 26 weeks a fundal height measurement of 23 to 29 centimeters would be considered normal.
Your regular obstetrician is unlikely to keep a careful record of a normal fundal height; they’ll probably only mention that it is normal or keep track of any abnormalities in fundal height. In large clinics, where a patient may see several different physicians during the course of her pregnancy, fundal height is an important measurement because it serves as an objective frame of reference among various doctors.
Larger Than Normal Fundal Size
If your physician discovers your fundal height measurement is increasing more rapidly than expected, an ultrasound or similar testing will likely be ordered to determine what’s causing the increase. According to the Mayo Clinic, some reasons for a larger than normal fundal height or a measurement that increases faster than expected include:
- A thicker than average uterus
- A thicker than average abdominal wall
- A full bladder
- Short height
- Rapid fetal growth
- Excessive amniotic fluid
- Uterine fibroids that may increase the risk of miscarriage
- Twins or other types of multiple birth
Smaller Than Normal Fundal Size
Conversely, your obstetrician may also require further testing if your fundal measurements are less than average. The Mayo Clinic reports some reasons for a smaller than expected fundal height or a measurement that increases more slowly than expected include:
- Well-conditioned abdominal muscles
- A slim or tall build
- A baby descending into the uterus prematurely
- A baby in breech position
- Too little amniotic fluid
- Intrauterine growth restriction
- A baby that’s physically small
Another possibility for a fundal height measurement is an error in the estimated date of conception, or the estimated date of pregnancy based on the first day of the last menstrual period. This isn’t uncommon and will cause a discrepancy between fundal height and the fetus' gestational age. If the fundal height measurement isn’t within the expected parameters, your physician will ask questions and perform additional testing to determine any problems that need to be addressed.
