Using a simple tape measure and recording the distance between the pubic symphysis and the fundus, or top of the uterus, is a quick, non-invasive and objective way to assess the likelihood of problems in a pregnancy.
The measurement from each prenatal visit can be compared as a rough indicator of growth and development of the uterus and the baby inside. It is usually measured in centimeters, and in an average pregnancy, the length in centimeters roughly equals the number of weeks a woman has been pregnant.
Fundal height tends to be used widely in large clinics, where a patient may be seen by different doctors, so an objective point of reference is needed. It is not as accurate as ultrasound in predicting fetal size or age, but ultrasound estimates can also vary and ultrasound vibrations may have some negative effects.
There may be cause for concern if the measurements deviate too far from the norm, which is based on standard charts. While it is true that some women tend to have bigger/smaller bellies and babies and may be perfectly healthy, a measurement varying from the average by more than 3 or 4 centimeters, especially if there is a widening discrepancy, alerts a doctor to the possibility of problems.
If Measuring 'Small for Date'
Measuring a little on the low side isn't necessarily bad. The way a woman carries a baby varies with size, stature, and the strength of abdominal muscles. Some women measure consistently small and then seem to pop out later in pregnancy. The baby may be turned sideways in mid-pregnancy, or the head may have dropped further into the pelvis late in pregnancy.
However, measuring small could indicate "oligohydramnios" or a lower than normal amount of amniotic fluid. Or it may suggest that the fetus is "growth restricted" or "growth retarded" as a result of insufficient blood flow from the placenta or maternal disease.
The article "Intrauterine Growth Restriction: Identification and Management" by Dr. David Peleg, published in the August, 1998 issue of American Family Physician states that intrauterine growth restriction or IUGR affects about 1 pregnancy in 20, and should be monitored to prevent growth problems or stillbirth. Although most small babies have not suffered from IUGR, and it is difficult to make an absolute diagnosis until the baby is born, the possibility of IUGR should not be taken lightly.
Usually ultrasound is used to monitor cases in which IUGR is suspected. In some cases IUGR warrants induction or a caesarean section.
If Measuring 'Large for Date'
Measuring a little on the high side could be a cause for either bragging rights or concern, depending on other test results. An unusually large fundal height could mean that the due date is off or the baby is in a breech position. Looser abdominal muscles, a result of earlier pregnancies, or "polyhydramnios," an excessive amount of amniotic fluid, may also contribute.
A higher than average measurement could indicate the presence of uterine fibroids or placenta previa. Or the baby could be large for gestational age as a result of gestational diabetes. If identified and treated early, gestational diabetes is usually less serious.
Hopefully, knowing more about fundal height measurements will help to prevent unnecessary worry and provide reassurance as to the standard of prenatal care being received.
