The Growth-Restricted Infant

Chapter 70 The Growth-Restricted Infant



Christiana R. Farkouh, MD, MPH




Medical Knowledge and Patient Care



Background and Definition


Intrauterine growth restriction (IUGR) represents a deviation and reduction in the expected fetal growth pattern. Fetal growth restriction complicates 5% to 8% of all pregnancies. IUGR is associated with a higher incidence of pregnancy complications, including stillbirth, prematurity, and perinatal morbidity and mortality. Often the terms small for gestational age (SGA) and IUGR are used interchangeably, but incorrectly. The critical distinction in the difference between SGA and IUGR is in the fetal growth potential. An SGA infant is one whose birth weight is below the 10th percentile, whereas an IUGR infant has failed to meet his or her growth potential or has shown a deceleration in the growth pattern during gestation.


The multiple causes of IUGR can be divided into three major categories of origin: fetal, placental, and maternal. Approximately 40% of cases of IUGR have no identifiable cause. Traditionally IUGR has been divided into symmetric or asymmetric growth restriction. The distinction between the two may relate to the timing of an intrauterine insult, as well as the possible cause and indeed even the severity of any inciting factor, but it is unclear if this distinction alone is tied to ultimate outcome.


Symmetric IUGR refers to any infant with a decrease in all parameters of weight, length, and head circumference. It is generally considered to be due to an event or process that occurs early in the pregnancy. Infants with asymmetric IUGR have decreased weight and length but demonstrate a relative head sparing; this event or process is believed to occur later in pregnancy.



Fetal Factors


Fetal factors that can impact in utero growth include chromosomal abnormalities such as trisomy 21, 18, or 13 or Turner syndrome. Genetic syndromes, including Russell-Silver and Cornelia de Lange as well as congenital malformations, multiple gestations, and congenital infection, have been associated with intrauterine growth restriction. The viral infections associated with IUGR have been given the acronym TORCH: toxoplasmosis, other (syphilis and other viruses), rubella, cytomegalovirus (CMV), and herpes.



Placental Factors


Placental factors that are associated with an increased risk for development of IUGR include abnormal placental implantation (velamentous cord insertions, previa, abruption), abnormal morphology, placental lesions, placental infarction, and placental infection.



Maternal Factors


Maternal factors that can impact fetal growth include chronic medical conditions such as diabetes, vascular diseases, auto immune diseases, hemoglobinopathy, hypertension, and preeclampsia. These chronic medical conditions can affect uterine blood flow as well as placental development and function. Factors related to maternal constitutional factors such as prepregnancy weight as well as weight gain during pregnancy correlate with fetal growth. Maternal cigarette, alcohol, drug (cocaine, heroin), and certain medications (warfarin, tretinoin [Retin-A]) use have all been associated with poor fetal growth both by the direct impact that these exposures have on placental function and also as a correlate of maternal nutrition. In addition, a prior history of a pregnancy complicated by IUGR, stillbirth, and/or spontaneous abortion is associated with an increased incidence of IUGR in a subsequent pregnancy.


Both term and preterm infants may manifest intrauterine growth restriction. The ultimate long-term outcome relates not only to the gestational age at birth but also the etiology, as well as the degree of the growth restriction. The incidence of perinatal morbidities correlates with the severity of the growth restriction. Morbidities such as respiratory distress syndrome, perinatal asphyxia, hyperviscosity-polycythemia syndrome, immunodeficiency, and metabolic derangements such as hypoglycemia, hypothermia, and hypocalcemia all occur at greater frequency in infants with IUGR compared with their appropriate-for-gestational-age (AGA) counterparts. The potential neurodevelopmental long-term outcomes associated with IUGR infants manifest as motor issues such as cerebral palsy, as well as learning and behavioral problems and altered postnatal growth.


Epidemiologic studies have demonstrated that altered fetal growth may be associated with the development of adult diseases such as insulin resistance, type 2 diabetes mellitus, obesity, hypertension, and cardiovascular disease. It has been hypothesized that the developmental adaptations that occur as a result of the altered fetal growth permanently alters postnatal physiology. This period of fetal development represents a period of rapid cell division, during which an insult or stressor may have long-lasting consequences on the tissue or organ function. This hypothesis is referred to the Barker hypothesis or the fetal origins hypothesis.

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Jul 18, 2016 | Posted by in PEDIATRICS | Comments Off on The Growth-Restricted Infant

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