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Intrauterine Growth Restriction

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KEY POINTS
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Key Points

  • Intrauterine growth restriction (IUGR) is commonly defined as a birth weight less than the 10th percentile at a given gestational age. It has also been defined as a fetus that has not reached its growth potential at a given gestational age.

  • Small for gestational age (SGA) describes a population of fetuses with a weight below the 10th percentile without reference to the cause.

  • Prenatal ultrasonography is the imaging method of choice for diagnosing and evaluating possible cases of IUGR. The typical finding is a significant discrepancy in some or all of the fetal biometric parameters as compared with measurements expected based on gestational age alone.

  • Because sonographic prediction of fetal weight may vary by up to 20% from actual fetal weight, diagnosis and management of IUGR is generally guided by serial sonographic assessments of the fetus.

  • Pregnancy management depends on the gestational age, the etiology of the IUGR, and the results of fetal surveillance. Fetal testing including Doppler studies and serial growth scans are important for determining whether a pregnancy can be continued expectantly.

  • Detailed Doppler assessment including umbilical arterial, middle cerebral arterial, ductus venosus, and umbilical venous assessments are used to evaluate fetal status, and may be used to optimize timing of delivery.

  • Gestational age at delivery is a strong predictor of neonatal outcome in IUGR cases.

  • Elective delivery is recommended for all cases of IUGR reaching 37 weeks of gestation, while expectant management with close fetal surveillance is recommended for cases less than 34 weeks of gestation. For cases between 34 and 37 weeks of gestation, management is individualized depending on overall fetal status.

  • A previous pregnancy complicated by IUGR is considered a risk factor for developing IUGR in a subsequent pregnancy. Such cases of recurrent IUGR usually reflect an underlying maternal medical problem, such as chronic hypertension or antiphospholipid antibody syndrome.

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CONDITION
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Intrauterine growth restriction (IUGR) is commonly defined as a birth weight less than the 10th percentile at a given gestational age (Table 123-1). It has also been defined as a fetus that has not reached its growth potential at a given gestational age, because of one or more causative factors (Lin and Santolaya-Forgas, 1998). The population from which expected fetal growth standards are derived to define the 10th percentile is of major importance. A review of all publications in the English language literature since 1963 that presented values for the 10th percentile of birth weight for gestational age has been published (Goldenberg et al., 1989). It was found that studies differed in how gestational age was determined, types of infants excluded, populations studied, and whether they were controlled for the sex of the infant as well as the race and parity of the mother. The 10th percentile birth weights at each gestational age from these various published standards differed substantially.

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