Excerpt from Fetal Growth Restriction
Synonyms, Key Words, and Related Terms: intrauterine growth retardation, IUGR, small for gestational age, SGA, intrauterine growth restriction, perinatal mortality, perinatal morbidity, birth defect, pregnancy, fetal death, prematurity, premature infant, neonatal death, fetal compromise, neonatal morbidity, caesarean delivery, caesarean section, cesarean delivery, cesarean section, C-section, brain-sparing effect, fetal growth retardation, imminent fetal demise, fetal compromise, complicated pregnancy, pregnancy complications, emergency delivery
Intrauterine growth restriction (IUGR) refers to a condition in which a fetus is unable to achieve its genetically determined potential size. This functional definition seeks to identify a population of fetuses at risk for modifiable but otherwise poor outcomes. This definition intentionally excludes of fetuses that are small for gestational age (SGA) but are not pathologically small. SGA is defined as growth at the 10th or less percentile for weight of all fetuses at that gestational age. Not all fetuses that are SGA are pathologically growth restricted and, in fact, may be constitutionally small. Similarly, not all fetuses that have not met their genetic growth potential are in less than the 10th percentile for estimated fetal weight (EFW). Of all fetuses at or below the 10th percentile for growth, only approximately 40% are at high risk of potentially preventable perinatal death (see Media file 1). Another 40% of these fetuses are constitutionally small. Because this diagnosis may be made with certainty only in neonates, a significant number of fetuses that are healthy but SGA will be subjected to high-risk protocols and, potentially, iatrogenic prematurity. The remaining 20% of fetuses that are SGA are intrinsically small secondary to a chromosomal or environmental etiology. Examples include fetuses with trisomy 18, cytomegalovirus infection, or fetal alcohol syndrome. These fetuses are unlikely to benefit from prenatal intervention, and their prognosis is most closely related to the underlying etiology. The clinician's challenge is to identify IUGR fetuses whose health is endangered in utero because of a hostile intrauterine environment and to monitor and intervene appropriately. This challenge also includes identifying small but healthy fetuses and avoiding iatrogenic harm to them or their mothers.
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