The term large for gestational age (LGA) can be confusing and scary, for some women. Thefundal height measurementis typically used once a pregnant woman starts showing. It is the measurement from the pubic bone to the top of the uterus. The measurement is noted in centimeters (cm) and should be around the same number as your current week of gestation. For instance, if you are 35 weeks pregnant your fundal measurement should be 35. However, the measurement of fundal height is NOT 100% accurate and should NOT be used as a sole diagnostic tool.
Why Does the Measurement Change?
When you lay in bed at night you toss and turn from one side to the other. Sometimes you pull your feet in and your knees stick up in the air and other times you lay on your side with your knees pulled to your chest. If you took measurements of your body height multiple times in one night you would notice extreme changes because you move. Baby moves too and fundal height changes with that movement. All baby has to do is roll one way and you are measuring small for gestational age. Roll the opposite way with knees facing the front of the uterus and the measurement is suddenly much larger than it was before. For this reason, there is a range which doctors use to separate issues that need to be addressed with further testing from common fundal height changes. Generally, measurements plus or minus three cm are considered normal.
There are several reasons you could be measuring LGA, including being overweight at the time of pregnancy and gaining more weight than suggested. A multiple pregnancy will also cause an irregular growth measurement that can be drastic well before the final weeks of pregnancy. By the 30th week of pregnancy, I was measuring 60 cm, but my twins also weighed nearly seven pounds each at birth just a couple weeks later.