Fundus Measurement in Pregnancy: What You Need to Know

Question
I am currently 31 weeks pregnant. My fundus was measured at 29 weeks and it was 28cm. What does this mean and is it accurute with my due date. I have read that I should have measured at 29cm. Please explain the purpose of the fundus and how accurate the measurements are. And is it consistent with my conception date. Thanks!!!


Answer
Dear Detra,

The fundus is simply the main body of the uterus. The measurement of the size of the uterus has been a reliable way to document the progression of growth of the baby for many years; the measurement also gives an indication as to how far along the pregnancy is.  Of course, one can't measure the entire size of the uterus from examining the abdomen, because some of the uterus lies below the pubic bone, into the pelvis.  The best one can do is measure from the pubic bone to the top of the uterus that can be felt.  Since all of the growth of the baby is in this part of the uterus anyway (the fundus, or body of the uterus), neglecting the cervix in the measurement isn't a big deal.

The fundal height - measured from the top of the pubic bone to the top of the uterus - is measured in centimeters, and it's a measurement that should increase as the pregnancy continues toward your due date. Even though the fundal height is generally a diagnostic tool held over from the days before ultrasound, it is still useful in large clinics where the same patient may not get the same doctor twice in a row for her prenatal visits.

There is no measurement more exact than ultrasound, and even this isn't perfect. But the fundal height provides a standard, reliable guideline and is fast, easy, and free for patients. As a general rule, the fundal height has "milestone" measurements. At 12 weeks, it should reach over the symphysis pubis, be at the umbilicus at 20 weeks and at the xyphoid process at 36 weeks. After 25 weeks the measurement in cms should approximately equal the number of weeks gestation. (26 weeks along = 26 cms)

For the most part, we use the measurement as a tool which might indicate an issue with fetal growth. If the fundal height is not progressing from one visit to the next, it may raise a red flag as to whether the baby is growing as he/she should be. That would then lead a doctor to order an ultrasound. OR if the height were to grow too much from one visit to the next or be consistently more than it should be, it might lead a doctor to suspect a multiple pregnancy or a LGA (large for gestational age) baby and again an ultrasound would be indicated.

Your measurement at slightly under what we'd expect (28cm at 29 wks) is not a red flag in and of itself. As long as your fundal height continues to grow appropriately, everything is fine. At approximately 36 weeks, the height is expected to drop (when baby drops lower into the pelvis).

I hope this information has helped you and answered your question. I wish you well!

Brenda