Clinical Review

Fetal growth restriction

OBG Manag. 2004 June;16(6):48-64

References

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3. Individualized managementAntepartum treatment

The question of bed rest. At present, there are no grounds for recommending strict bed rest in FGR cases. A Cochrane review³⁰ showed no improvements with hospitalized bed rest compared with ambulation. Prolonged rest increases risk of thromboembolism and can be costly and inconvenient.

Nutritional remedies. Of the options that have been tested, which include high protein supplementation, nutrient supplementation such as beef liver extract, and balanced energy/protein supplementation, only the last (with protein content comprising less than 25% of total energy content) has led to a significant reduction in SGA births.^31-33

Other approaches. We lack reliable evidence that other interventions such as oxygen administration, abdominal decompression, and pharmacological agents, including calcium channel blockers, beta mimetics, and magnesium, are beneficial or effective in improving or preventing FGR.

A meta-analysis³⁴ of 13 trials involving more than 13,000 women showed that early aspirin treatment reduced the risk of FGR but failed to improve outcome. A more recent meta-analysis³⁵ of 38 trials of aspirin in highrisk pregnancies found no reduction in the incidence of FGR or perinatal death, although a reduction in risk of preterm births was noted.

Etiologic management

Most etiologic conditions are either not amenable to therapy or fetal growth is not improved by treatments that benefit the mother. An example is maternal hypertensive disease, in which the indicated treatment has no beneficial effect on fetal growth.

Treatment of poor lifestyle habits may be helpful. If the mother smokes, vigorous smoking-cessation education and counseling is urged. Also address alcohol consumption and other substance abuse, and offer remedial measures.

The diagnosis of fetal viral and parasitic infections is important for prognostication and neonatal management. Although few perinatal infections are treatable in utero, maternal therapy may prevent certain infections from spreading to the fetus. Examples include toxoplasmosis and malaria.

If lethal malformations or lethal aneuploidy are identified prenatally, avoid fetal surveillance and unnecessary intervention, which may expose the mother to unnecessary and unjustifiable risks.

Fetal surveillance strategy

If fetal biometry indicates fetal weight below the 10th percentile, begin fetal surveillance. The current standard, umbilical arterial Doppler sonography, is the primary test in sonographically documented growth restriction. Also assess amniotic fluid volume—as part of the BPP or independently. AFI is the most commonly used BPP tool.

In the United States, the nonstress test traditionally is the primary monitoring modality, with the BPP as backup, although the BPP—which includes the NST—has been recommended as the primary test.

Normal Doppler findings. When the Doppler index remains within normal limits or does not progressively rise, weekly testing should suffice, with the NST or BPP as backup or in conjunction with Doppler.

If fetal and maternal conditions remain reassuring, allow the pregnancy to continue to maturity and assess the patient for delivery. Postdate pregnancy is not advised in the presence of sonographically confirmed growth compromise.

A high or increasing Doppler index warrants more intensive fetal surveillance consisting of weekly umbilical arterial Doppler and once- or twice-weekly NST and BPP until fetal maturity.

If these tests indicate fetal compromise, or absent end-diastolic velocity develops, the likelihood of poor perinatal outcome is increased and an urgent clinical response is indicated. Hospitalize the patient and individualize management, depending on gestational age and fetal status.

Optimal timing of delivery

The optimal timing of delivery in a preterm pregnancy with FGR is unclear. A recent multicenter randomized controlled trial, the Growth Restriction Intervention Trial (GRIT),³⁶ compared 2 strategies: delivery within 48 hours with steroid administration or delivery delayed as long as fetal status permits. The population consisted of high-risk gravidas between 24 and 36 weeks’ gestation. More than 90% of the women had pregnancies complicated by FGR. No significant differences were noted between the 2 groups in stillbirth rates.

Fortunately, thanks to recent advances in perinatal care, a management strategy can be recommended:

At or near term (34 weeks or beyond), the absence of end-diastolic flow in the umbilical artery should prompt consideration of immediate delivery.

Other ominous findings that prompt such consideration include:

Cessation of fetal growth on successive ultrasound examinations
Progression of umbilical arterial absent enddiastolic flow to reversed end-diastolic flow
Nonreassuring heart rate patterns including nonreactive NST, poor fetal heart rate baseline variability, and persistent variable or late decelerations
Oligohydramnios
BPP score of 4 or below

Less than 34 weeks. When absent enddiastolic flow develops in a preterm pregnancy with a significant risk of fetal lung immaturity, seek further assurance of fetal well-being via daily surveillance with umbilical arterial Doppler sonography, nonstress test, and biophysical profile. Administer betamethasone to enhance fetal lung maturity. Delivery is indicated regardless of maturity when a single test or combination indicates imminent fetal danger and the fetal risk from a hostile intrauterine environment is judged to be greater than that from pulmonary immaturity.