A fundal height measurement helps estimate the size of a fetus during pregnancy. In general, the measurement is defined as the distance in centimeters from the pubic bone to the top of the uterus.
After week 24 of pregnancy, the fundal height generally is expected to match the number of weeks of pregnancy — plus or minus 3 centimeters. For example, if you're 27 weeks pregnant, your healthcare professional would expect your fundal height to be about 27 centimeters.
Some factors can make a fundal height measurement less accurate. They include obesity and a history of common growths in the uterus called fibroids. Also, fundal height measurements tend to be less accurate after 36 weeks of pregnancy.
A fundal height that is smaller or larger than expected — or that changes faster or slower than expected — may signal:
- Slow growth of a fetus. The medical term for this condition is fetal growth restriction.
- A pregnancy with more than one fetus.
- Too little amniotic fluid, also called oligohydramnios.
- Too much amniotic fluid, also called polyhydramnios.
If your fundal height is different than expected, your healthcare professional might suggest an ultrasound imaging test. An ultrasound can help find out what's causing the unusual measurements. Ultrasound also can be used to track your pregnancy more closely.
Fundal height is only a tool to estimate a fetus's growth in the womb. It's not an exact science. But fundal height measurements can offer reassuring signs of steady growth. If you're concerned about your fundal height measurements, talk to your healthcare professional.