Interpretation of fundal height measurements

Changes of Fundal Height in Normal Pregnancy

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).About five months (20-22 weeks), the top of the uterus is usually right at the mother's bellybutton (umbilicus or navel) and at eight to nine months (36-40 weeks), the top of the uterus is almost up to the bottom of the mother's ribs. Why may fundal height drop lower in the weeks just before birth? Because the fetal head (part) goes down to the pelvic.

If there is any deviation of the fundal height from the above-given areas with the corresponding weeks of gestation, it will indicate something is wrong which could be whether from the maternal side or the fetus.

Causes of Abnormal Uterine Growth

If the measure of the size of the fundal height is not what you expect based on the mother's LMNP, it could mean one or more of the following.

a) A wrong due date

There are several reasons why a due date calculated 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 be less pregnant than you thought, so the uterus is smaller than you expect.
  
• Sometimes a woman has a little bleeding after she gets pregnant. If she assumed that was her LNMP, this woman would be one or two months more pregnant than you thought. The uterus will be bigger than you expect.
  

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.

b) If the uterus grows more than two finger-widths a month or more than 1 cm a week, several different causes are possible.

• The mother may have twins, had diabetes in a past pregnancy, her past babies was born very big (more than 4 kilograms), or was ill or died at birth and no one knows why (you have learned in study session-9),the mother may have diabetes (you have learned in study session-9),the mother may have too much water (amniotic fluid) in the uterus. These conditions make the uterus bigger than expected.
  
• Too much water (amniotic fluid) is not always a problem, but it can cause the uterus to stretch too much and make it bigger resulting in poor contraction to push the baby out, or to stop the bleeding after the birth.
  
• In such cases (the uterus is measuring too big, and you do not suspect twins), try to refer the woman to the nearest health facility that can give her a sonogram (ultrasound examination).
  
• The mother may have a molar pregnancy (a tumour instead of a baby). Sometimes a woman gets pregnant, but a tumour grows instead of a baby called a molar pregnancy. In such cases, blood spotting and tissue (sometimes shaped like grapes) may be discharged from her vagina
  

Other signs of a molar pregnancy are that:

c) The uterus is growing too slowly

Slow growth uterus can be a sign of one of these problems:

• The mother may have too little water (amniotic fluid) in the uterus; she may have a poor diet.
  
• The mother may have high blood pressure (hypertension). High blood pressure can keep the baby from getting the nutrition it needs to grow well. You learned how to check her blood pressure in the previous study session.
  
• If the mother is used to drinking alcohol, smoking, or using drugs, these can cause a baby to be small.
  
• The fetus may be dead because dead fetus will not grow, the uterus stops getting bigger.
  

Confirm whether the fetus is dead or not:

• If the mother is five months pregnant or more, ask if she has felt the fetus moves or not recently. If the fetus has not moved for two days, something may be wrong.
  
• If the mother is more than seven months pregnant and you are unable to listen to the fetal heart beat, or if you heard the baby's heartbeat on an earlier visit and not now, suspect fetal death.
  
• 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 ever, and so the risk of infection.