In this study session, you will learn how to carry out an important measurement that should be done at every antenatal visit — measuring the height of the top of the mother’s uterus as a way of assessing whether her baby is growing normally. We teach you two ways of doing this — using your fingers, and using a soft measuring tape. This will enable you to estimate the stage of pregnancy she has reached, and check the accuracy of the due date calculated from the mother’s last normal menstrual period. Then we discuss possible reasons for the uterus growing too quickly or too slowly, and what actions you should take if you suspect that something may be wrong.
When you have studied this session, you should be able to:
10.1 Define and use correctly all of the key words printed in bold. (SAQ 10.1)
10.2 Know how to measure fundal height using the finger method and a soft measuring tape. (SAQ 10.1)
10.3 Interpret fundal height measurements to assess normal fetal growth in relation to gestational age. (SAQ 10.2)
10.4 Identify possible causes of abnormal fundal height measurements and take the appropriate actions. (SAQ 10.3)
The purpose of measuring the height of the mother’s uterus is to determine if the baby is growing normally at each stage of the pregnancy. When you measure the uterus, you check to see where the top of the uterus is.
Do you remember what the domed region at the top of the uterus is called? (You learned this in Study Session 3.)
It is called the fundus.
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. Measuring the fundal height will show you three things:
As the baby grows inside the uterus, you can feel the uterus grow bigger in the mother’s abdomen. The top of the uterus moves about two finger-widths or 4 cm higher each month (Box 10.1).
At about three months (13-14 weeks), the top of the uterus is usually just above the mother’s pubic bone (where her pubic hair begins).
At about five months (20-22 weeks), the top of the uterus is usually right at the mother’s bellybutton (umbilicus or navel).
At about eight to nine months (36-40 weeks), the top of the uterus is almost up to the bottom of the mother’s ribs.
Babies may drop lower in the weeks just before birth. You can look back at Figure 7.1 in Study Session 7 to see a diagram of fundal height at various weeks of gestation.
To feel the uterus, have the mother lie on her back with some support under her head and knees. Explain to her what you are going to do (and why) before you begin touching her abdomen. Your touch should be firm but gentle. Walk your fingers up the side of her abdomen (Figure 10.1) until you feel the top of her abdomen under the skin. It will feel like a hard ball. You can feel the top by curving your fingers gently into the abdomen.
If the top of the uterus is below the bellybutton, measure how many fingers below the bellybutton it is. If the top of the uterus is above the bellybutton, measure how many fingers above the bellybutton it is.
Look carefully at Figure 10.2. If the baby is growing normally, by how many finger-widths should the uterus rise in the second trimester (3-6 months of pregnancy, or 15-27 completed weeks of gestation)?
Fundal height should increase by 6 finger-widths (two finger-widths every month) in the second trimester.
How many fingers above the bellybutton should the top of the uterus be at 7 months’ gestation?
See Figure 10.3 for the answer.
How do you explain the position of the dotted line at 9 months in Figure 10.2, which is below the line showing fundal height at 8½ to 9 months?
Babies may drop lower in the weeks just before birth (look back at Box 10.1).
Look at the diagrams in Figure 10.4 (a) and (b). How many weeks pregnant is the woman in each case, based on the finger method of measuring fundal height shown in Figure 10.2?
In Figure 10.4(a) the woman is about 4½ months pregnant. In Figure 10.4 (b) she is about 6½ months pregnant (three fingers above the bellybutton).
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 antenatal 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 would you record the measurements shown in Figure 10.4(a) and (b)?
The measurement in Figure 10.4(a) would be recorded as -2. The measurement in Figure 10.4(b) would be +3.
You need to be aware that the finger method for estimating gestational age (the number of weeks/months of pregnancy) has some limitations that affect its accuracy.
Look at your own hands. 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?
Because of the big variation in the thickness of our fingers, there could be up to three weeks difference between the fundal height measurement of the same woman made by two different people. (This is known as ‘inter-observer variation’, i.e. variation between different observers.)
Even if the same health worker measures the fundal height of the same woman several times on the same day, the answer may be different each time, because the finger method is not very precise. (This is known as ‘intra-observer variation’, i.e. variation by a single observer at different times.)
Finally, you might have realised that the distance between the symphysis pubis (pubic bone) and the umbilicus (bellybutton) varies between women when they are not pregnant, and this variation affects the accuracy of the fundal height measurement using the finger method. For example, it assumes that the distance between the pubic symphysis and the umbilicus is 20 cm at 20 weeks’ gestation, but it can be as long as 30 cm and as short as 14 cm.
To overcome these limitations, it is recommended that you measure fundal height using a soft tape measure if you have one, as described next.
You can use this method when the top of the uterus grows as high as the woman’s bellybutton.
During the second half of pregnancy, the size of the uterus in centimetres is close to the number of weeks that the woman has been pregnant. For example, if it has been 24 weeks since her last normal menstrual period, the uterus will usually measure 22-26 cm. The uterus should grow about 1 cm every week, or 4 cm every month.
Doctors, nurses and many midwives are taught to count pregnancy by weeks instead of months. They start counting at the first day of the last normal menstrual period (LNMP), even though the woman probably got pregnant two weeks later. Counting this way makes most pregnancies 40 weeks long (or you can say a normal gestation is 40 weeks).
If you are measuring correctly and you do not find the top of the uterus where you expect it to be, based on the date the woman gave you for her LNMP, it could mean three different things:
There are several reasons why a due date figured from the LNMP could be wrong. Sometimes women do not remember the date of their LNMP correctly. Sometimes a woman misses her menstruation for another reason, and then gets pregnant later. This woman could really be less pregnant than you thought, so the uterus is smaller than you expect. Or sometimes a woman has a little bleeding after she gets pregnant. If she assumed that was her LNMP, this woman will be one or two months more pregnant than you thought. The uterus will be bigger than you expect.
Remember due dates are not exact. Women often give birth up to 2 or 3 weeks before or after their due date. This is usually safe.
If the due date does not match the size of the uterus at the first visit, make a note. Wait and measure the uterus again in two to four weeks. If the uterus grows about two finger-widths or 1 cm a month, the due date that you got from feeling the top of the uterus is probably correct. The due date you got by counting from the LNMP was probably wrong.
If the uterus grows more than 2 finger-widths a month, or more than 1 cm a week, several different causes are possible:
If you think there might be twins, even if you can find only one heartbeat, refer the woman to the nearest health centre.
It can be very difficult to know for sure that a mother is pregnant with twins. Signs of twins are that:
We will show you how to listen to the fetal heartbeat through the mother’s abdomen in Study Session 11. For now, we are focusing on twins as a possible reason for the uterus being larger than expected. Here are two ways to try to hear the heartbeats of twins:
Because twin births are often more difficult or dangerous than single births, it is safer for the woman to go to a hospital to give birth. Since twins are more likely to be born early, the mother should try to have transportation ready at all times after the 6th month. If the hospital is far away, the mother may wish to move closer in the last months of pregnancy. Be sure to have a plan for how to get help in an emergency.
You learned about the warning signs of diabetes in Study Session 9.
If a woman had all the warning signs of diabetes, what would you expect to find?
Refer the woman to a health centre if you suspect she may have diabetes.
She had diabetes in a past pregnancy. One of her past babies was born very big (more than 4 kilograms), or was ill or died at birth and no one knows why. She is fat. She is thirsty all the time. She has frequent itching and a bad smell coming from her vagina. Her wounds heal slowly. She has to urinate more often than other pregnant women. Her uterus is bigger than normal for how many months she has been pregnant. She has sugar in her urine when you do the dipstick test (Section 9.8.1 of Study Session 9).
Too much water (amniotic fluid) is not always a problem, but it can cause the uterus to stretch too much. Then the uterus cannot contract enough to push the baby out, or to stop the bleeding after the birth. In rare cases, it can mean that the baby will have birth defects. Try to refer the woman to the nearest health facility that can give her a sonogram (ultrasound examination) if the uterus is measuring too big and you do not suspect twins.
Sometimes a woman gets pregnant, but a tumour grows instead of a baby. This is called a molar pregnancy (Figure 10.7). Blood spotting and tissue (sometimes shaped like grapes) may be discharged from her vagina.
If you detect the signs and symptoms of a molar pregnancy, refer the woman to a hospital as soon as possible. The tumour can become a cancer and kill her, sometimes very quickly. A surgeon can remove the tumour to save the woman’s life.
Other signs of a molar pregnancy are that:
Slow growth can be a sign of one of these problems:
If you do not have the right equipment to check her blood pressure, and the uterus is growing too slowly, refer her to the nearest health centre for evaluation.
If you suspect that the baby may have died, refer the mother to a health centre for the stillbirth.
If the mother is five months pregnant or more, ask if she has felt the baby move recently. If the baby has not moved for two days, something may be wrong. If the mother is more than seven months pregnant, or if you heard the baby’s heartbeat at an earlier visit, listen for the heartbeat again.
If the woman reports no fetal movements and you cannot hear the heartbeat, the baby may have died. If so, it is important for a dead baby (stillbirth) to be delivered soon, because the woman may bleed more than other mothers, and she is at more risk of infection.
When a mother loses a baby, she needs love, care and understanding (Figure 10.8). Make sure that she does not go through labour alone. If she gives birth to a dead baby in the hospital, someone she trusts should stay there with her during the birth.
In this study session, you have learned how to measure the fundal height, using your fingers and a measuring tape. You have also learned to interpret of your measurements and take the appropriate actions. In the next study session you will learn how to assess the position of the baby by palpating (feeling) the mother’s abdomen and listening to the position of the fetal heartbeat.
In Study Session 10, you have learned that:
Now that you have completed this study session, you can assess how well you have achieved its Learning Outcomes by answering the questions below Case Study 10.1. Write your answers in your Study Diary and discuss them with your Tutor at the next Study Support Meeting. You can check your answers with the Notes on the Self-Assessment Questions at the end of this Module.
Abebech is a pregnant woman, whose duration of gestation based on her last normal menstrual period (LNMP) is six months. When you examine her, you can feel that the fundus is four finger-widths above her bellybutton and you can hear a fetal heartbeat clearly.
Is the gestational age of Abebech’s baby based on fundal height measurement consistent with the gestational age calculated from her LNMP?
The gestational age based on fundal height is one month more than expected from the date of the LNMP. Therefore, the uterus is bigger than expected from the date of the LNMP.
What possible explanations can you give for your findings in Abebech’s case, and what actions should you take?
The uterus may be bigger than expected because the date of the LNMP may be incorrect, and Abebech is really seven months pregnant. This is not a problem, but it is important to investigate other possible explanations. For example, she may have too much amniotic fluid (water) surrounding the baby in the uterus; you should refer her to a health facility where she can have an ultrasound examination to find out if this is the problem. Or she could have a twin pregnancy. You can hear one fetal heartbeat clearly, so get someone else to help you listen to Abebech’s abdomen to see if you can hear two fetal heartbeats. If you suspect she is having twins, refer her to the nearest health facility.