The purpose of measuring the height of the mother's uterus is to determine the gestational age and growth of the fetus at each stage of pregnancy. It also helps us to identify multiple pregnancies and complications of pregnancy e.g. amniotic fluid disorders, hydatidiform mole, and fetal growth disturbances. Between 20 to 34 weeks of gestation, the height of the uterus correlates closely with measurements in centimetres. 

Thus the fundal height measurement often matches the number of weeks. For example, if she is 24 weeks pregnant, you would expect the fundal height to be about 24 centimetres but your measure may be somewhat smaller or larger than expected. These causes will be discussed later.

When you measure how high the top of the uterus has reached in the mother's abdomen, you are measuring the fundal height. This is a much more accurate way of estimating fetal growth than weighing the mother.

We can understand three things from measuring the fundal height:

• Gestational age.
• The growth of the fetus.
• The expected date of delivery.

Methods of fundal height measurement

There are two methods of fundal height measurement:

a) The Finger method

One finger above umbilicus is equal to two weeks and below umbilicus one finger is equal to one week. If you felt, the uterus at symphysis it would correspond to 12 weeks; if at the umbilicus it is 20 weeks and at xymph-sternum it is 38 weeks.

1. Get her consent.
   
2. Have the mother lie on her back with some support under her head and knees.
   
3. Explain to her what you are going to do (and why).
   
4. Palpate her abdomen gently but firmly.
   
5. Walk your fingers up the side of her abdomen.
   
6. You can feel the top by curving your fingers gently into the abdomen.
   
7. Measure how many fingers below or above the umbilicus the fundus is located.
   
8. Record your findings.
   

(Fundal height should increase by 6 finger-widths (two finger-widths every month) in the second trimester

• When you measure fundal height at every antenatal visit, write down the number of fingers you used to measure the height of the uterus on the woman's ANC record card.
  
• Put a "+" (plus) sign in front of the number if the top of the uterus is above the bellybutton.
  
• Put a "–" (minus) sign in front of the number if the top of the uterus is below the bellybutton.
  

How to calculate the Fundal height:

Q. If you found the fundus of a pregnant mother above the umbilicus with 3 fingers measurement, what is the gestational age of this pregnancy? How could you record this in the ANC card?

A. The gestational age is 26 weeks because, if the fundus is found at the umbilicus, the gestational age is always 20 weeks. One finger above the umbilicus represents 2 weeks, 3 fingers represent 6 weeks. Thus, we add 20 weeks + 6 weeks = 26 weeks. When we record this on the ANC card, we write "3+".

Limitations of the finger method:

You need to be aware that, a finger method to measure the fundal height may have limitations. Can you suggest why the finger method might give a different estimate of gestational age if two different health workers used this method to measure the same woman's fundal height? The reason is there big variation in the thickness of our fingers which makes upto three weeks difference between the fundal heights measurements of the same woman made by two different people.

b) The Soft Tape measurement:

The soft tape measures from the symphysis to funded height in centimetres with a tape meter. This is accurate between 18-34 weeks to within two weeks of actual gestational age.

Steps for the measurement of the fundal height using soft tape meter (Figures 10.2 & 10.3):

1. Obtain the woman's consent.
   
2. Encourage the woman to empty her bladder if she didn't do it in the last 30 minutes.
   
3. Let the woman be in lying position with her leg extended(consider to put support from her right buttock not to compromise the fetal circulation to the inferior vena cava).
   
4. Ensure your hand is clean and warm.
   
5. Place the zero mark of the tape at the funds and measure to the symphysis by putting the tape midline to the woman's abdomen.
6. Document the distance in cm(if there is 2cm discrepancy) it warns you that there may be problem.