Fetal Surveillance
Unless delivery occurs, once treatment begins the fetus must undergo surveillance. The purpose of this is to identify further progression of the disease process that would jeopardize the fetus to a point that it would be better to be delivered than to remain in utero. There are four testing modalities, each of which addresses different aspects of surveillance, which are helpful. Most physicians agree that a combination of tests are better than an isolated test.
Non-Stress Test (I have two of these a week, at present)
This is one of the first tests used in the surveillance of IUGR fetuses and the simplest to perform. The physician uses a heart rate monitor to determine changes in the fetal heart rate with fetal movement. If the heart rate increases more than 15 beats for more than 15 seconds (at my current gestation, they look for an increase of 10 beats for more than 10 seconds), this is considered to be a reactive test. If the heart rate does not accelerate, remains flat, or decreases, then this is an abnormal test. The problem with this test is that it changes late in the course of the disease and does not identify a fetus with IUGR. When patients are diagnosed with IUGR and require continuous monitoring, the fetal heart rate tracing may be useful in detecting fetal distress.
Amniotic Fluid Index
The physician measures the vertical depth of four pockets of amniotic fluid to obtain a total amniotic fluid index. This method allows for comparison of changes in amniotic fluid with time. In the normal fetus the amniotic fluid index remains relatively constant. In the fetus with IUGR, it may decrease slowly, or decrease abruptly with time. A decrease in amniotic fluid may occur before there are changes in the non-stress test. The current recommendations are that if the amniotic fluid index decreases below 8 after 35 weeks, then delivery should be considered.(at yesterday's scan, I think my AFI was around 15, which is really good)
The following is an example of a fetus at risk for IUGR in which the amniotic fluid index was measured but the nurses and physician did not understand the principles of an abnormal reading. The fetus was allowed to remain in utero and developed cerebral palsy from oxygen deprivation. The family sued the hospital and the physician and was awarded 9.7 million dollars which was the largest malpractice award in the state of Utah.
This is the amniotic fluid index in the above case. The blue represents the normal range.
At 35 weeks the fluid measurement was 16. Four days later it dropped to 6.3. This sudden drop
was ignored by the nurses and physician caring for the patient. A few days later
the fetus was damaged because the umbilical cord was compressed, resulting in cerebral palsy.
Doppler of the Umbilical Artery
In a previous section I discussed Doppler evaluation of the umbilical artery. When IUGR is diagnosed, the value of sequential studies of the umbilical artery Doppler waveform is to determine if the Resistance Index is increasing or decreasing. If it is increasing, then this signifies a deteriorating condition. The following graph illustrates these principles.
This is a graphical display of the Resistance Index measurement of the umbilical artery
Doppler waveform If the measurement increases, this indicates the fetus is at increased risk
for adverse outcome.
Biophysical Profile (not sure if this is what they do on my Fridays, it's possible, although they haven't mentioned it)
This test combines the non-stress test and the amniotic fluid index with fetal movement, breathing, and muscle tone. If each of the tests are normal they are given a score of 2. If abnormal, a score of 0. If the score is 6 or less, this suggests the fetus is at risk for adverse outcome. While the biophysical profile is a useful test, when it becomes abnormal the fetus may have already suffered some damage.
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