Measuring fundal height during pregnancy

What is fundal height?

Fundal height is the distance from your pubic bone (symphysis pubic) to the top of your uterus (fundus). Taking a fundal height measurement is an easy, inexpensive method of checking to see that your baby is growing well. If you're pregnancy is considered high-risk, your provider is likely to forgo fundal height measurements and use ultrasounds to track your baby instead.

If you are getting your fundal height measured, remember that the measurement isn't used to estimate your due date – your last menstrual period and your first ultrasound exam will be used for that. But it can provide information about your baby's size as well as how much amniotic fluid is in your uterus. (Too much or too little amniotic fluid is uncommon, but it can put you at risk for complications.) 

The fundal height measurement isn't diagnostic (you wouldn't receive treatment based on a measurement that's off), but it's one way to screen for a problem with your pregnancy.

Your fundal height measurement changes as your pregnancy progresses. Here's a range of typical fundal height measurements during pregnancy:

• At 12 weeks, the fundus is at the level of the pubic bone.
• At 16 weeks, it's about halfway between the pubic bone and the belly button (the umbilicus).
• At about 20 weeks, it reaches the belly button.
• Beginning at 24 weeks, the measurement in centimeters should match (within a centimeter or two in each direction) the gestational age of your baby. So if you're 25 weeks pregnant, your fundal height should be about 23 to 27 centimeters.
• After 36 weeks, the fundal height may decrease as the baby engages in your pelvis (moves down) in preparation for labor.

About an hour after delivery, your uterus will go down to where it was at 20 weeks (around your belly button). After that, it will slowly return to its normal size by about 6 weeks.

Who will have their fundal height measured?  

Beginning around week 24, fundal height measurements are routinely taken at each prenatal visit for women who are having a low-risk pregnancy.

Women who are being monitored for a high-risk pregnancy (those who have high-risk conditions such as obesity, lupus, diabetes, and hypertension) usually don't have fundal height measurements taken. That's because they'll likely have ultrasounds to monitor their baby's growth throughout pregnancy. Ultrasounds are more accurate than fundal height measurements for assessing a baby's growth, so taking the fundal height is unnecessary for these women. 

What affects fundal height measurements?

Many things can affect fundal height measurements, but keep in mind that there isn't always a reason why someone's measurement is smaller or larger than expected. Your provider will probably schedule an ultrasound to find out what's going on/confirm your due date, but most of the time, the ultrasound is normal after a small or large fundal height measurement.

Measuring large for gestational age means your fundal height is more than 3 centimeters larger than expected for your stage of pregnancy, based on your due date. You could be measuring large for gestational age if:

• Your due date is off. (The ultrasound can help your provider figure out a more accurate due date.)
• You have looser abdominal muscles than most women, perhaps as a result of earlier pregnancies.
• You're overweight or obese, which can make it more difficult to get an accurate measurement.
• You have uterine fibroids.
• You're carrying twins or more.
• You have too much amniotic fluid (polyhydramnios).
• Your baby is in a breech or other unusual position.
• Your baby is much bigger than normal, a condition known as macrosomia. Risk factors for macrosomia include having type 1 or type 2 diabetes before pregnancy and gestational diabetes.

Measuring small for gestational age means your fundal height is more than 3 centimeters smaller than expected for your stage of pregnancy. Your fundal measurement might also be on the small side if:

• You have a small stature or well-conditioned abdominal muscles.
• Your baby has dropped into your pelvis in preparation for delivery.
• Your baby has intrauterine growth restriction.
• You have too little amniotic fluid (oligohydramnios).

How fundal height is measured by a provider 

The fundal height measurement is taken in centimeters using a measuring tape.

Your provider will have you lie flat on your back. They'll place one end of the measuring tape on your pubic bone and stretch the tape across your belly (lengthwise) to the top of your uterus. The number where the tape reaches the top of your uterus is your fundal height.

How to measure fundal height on your own

It can be tricky, even for experienced practitioners, to get an accurate fundal height number. But – as long as you don't put too much stock in it – there's no harm in trying. Here's how:

1. Lie down flat on your back.
2. Using a tape measure with centimeters marked, place the zero at your pubic bone.
3. Pull the tape over (and flat against) your stomach, towards the top of your uterus. The number where the tape reaches the top of your uterus (the hardest area at the top of the belly, where you can push your hand down) is your fundal height.

Should I be concerned about my fundal height measurement?

Definitely don't worry if your fundal height measurement is off by a centimeter or two – this is common and no cause for concern. This isn't an exact method, and it's easy for measurements to be off a bit.

Still, fundal height measurement is one screening tool that your provider can use to make sure that your baby is growing well and that your pregnancy is healthy. Your provider will also consider your obstetric history and other factors If they have any concerns about your measurement, they'll order an ultrasound right away to check on your baby's growth and the level of amniotic fluid. You also might need additional monitoring as your pregnancy progresses.

Learn more:

• Choosing a prenatal care provider
• When can I hear my baby's heartbeat?
• When can I find out my baby's sex?
• Prenatal tests