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MS WordPerinatologist Corner - C.E.U/C.M.E. Modules
Fetal Growth Restriction
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5. Read the material on management
Because the growth-restricted fetus is at risk of hypoxia, acidosis, and death, once F.G.R. has been diagnosed, heightened surveillance of fetal well-being would seem to be indicated. Delivery may be appropriate regardless of gestational age if reassuring fetal surveillance cannot be obtained. What is the best strategy to assure that the fetus is not in jeopardy? Is there any evidence that antenatal surveillance in pregnancies complicated by FGR improves outcomes? The best strategy initially would include a high-resolution ultrasound fetal anatomic survey to rule out anomalies and assess amniotic fluid volume.
Other diagnostic studies will depend on the maternal history of intercurrent exposure to possible infectious etiologies. Obtaining fetal karyotype and "TORCH" titers may then be appropriate in selected cases, but the etiology in most cases will remain elusive. Non-stress testing has been the mainstay of surveillance, but it has poor sensitivity and often may not become abnormal until late in the course of this disorder. There are no studies addressing the optimal time interval between tests.
At present there is also not enough evidence from randomized trials to evaluate the use of the biophysical profile as a test of fetal well-being. Doppler ultrasound, however, has been shown to be useful in this disorder. There is a temporal sequence in the deterioration of the various Doppler parameters in F.G.R. prior to the onset of fetal distress. This onset of abnormal Doppler findings usually follows this sequence: elevated umbilical artery P.I., decreased middle cerebral artery P.I., absent end-diastolic flow in the umbilical artery, increased resistance to flow in the ductus venosus, reversed flow in the umbilical artery, eventually followed by an abnormal non-stress test. These findings are thought to evolve over a course of approximately two weeks, but are variable.
The optimum timing of repeat testing is unknown, and remains dependent on the assessment of the severity of the F.G.R. The best evidence is that a normal umbilical artery to middle cerebral artery P.I. ratio has a 98% negative predictive value as regards I.U.F.D., and allows continued expectant management if the fetus is preterm.
Unfortunately, there is insufficient evidence from randomized trials of the benefit of any intervention for F.G.R. other than smoking cessation and treatment of malaria in infected women. Interventions of questionable or no efficacy include bed rest, nutritional supplementation, micronutrient supplementation, oxygen therapy, plasma volume expansion, and low-dose aspirin. Therefore, delivery is the best treatment for the mature fetus, but may be more problematic for the preterm fetus. It is important to put together the whole clinical picture and not just react to one abnormal ultrasound finding. Rather, decide if this fetus is actually at risk of I.U.F.D. and would do better in the nursery. If fetal surveillance is persistently non-reassuring, however, corticosteroid therapy for fetal lung maturation is appropriate, followed by delivery.
Many of these severely affected fetuses will not tolerate labor and a high rate of cesarean delivery may be anticipated. A positive contraction stress test may or may not predict which fetuses will tolerate labor. If oligohydramnios is present, variable decelerations may be anticipated, and amnioinfusion may be an appropriate strategy. Late decelerations reflect diminished placental function and are more difficult to remedy. Be sure oxygen delivery to the fetus is maximized. Optimizing maternal cardiac output through adequate hydration and lateralization, enabling her to have enough volume to best perfuse the placenta, can most physiologically effect this. Remember that maternal oxygen saturation is usually over 95%on room air, so don't count on supplemental oxygen to be able to significantly improve her oxygenation on this part of the curve, or enable her to transfer more oxygen to the fetus. Growth-restricted infants should be born in a facility with a nursery staff able to handle their various postnatal problems.
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