(1)
Department of Family Medicine, University of California, Riverside, Riverside, CA, USA
Key Points
1.
Intrauterine growth restriction (IUGR) is defined as fetal weight below the tenth percentile and an abdominal girth below the 2.5 percentile.
2.
Factors associated with IUGR can be categorized as fetal genetic, uterine environmental, maternal, toxic exposures, and constitutional.
3.
Complications associated with IUGR include early complications (increased mortality, pre-eclampsia, preterm labor, still birth) and late complications (learning, behavioral, and developmental abnormalities).
Background
Fetal growth is among the most important of parameters monitored during the course of prenatal care. Although the majority of pregnancies proceed with no complications in fetal growth, a small number will show evidence of growth restriction. A variety of conditions are associated with or increase the risk for intrauterine growth restriction (IUGR). These factors are summarized in Table 6.1.
Table 6.1
Risk factors for intrauterine growth restriction (IUGR)
|
Fetal-genetic factors |
|
Chromosomal abnormalities (e.g., trisomy 21) |
|
Neural tube defects |
|
Achondroplasia |
|
Osteogenesis imperfecta |
|
Gastrointestinal (gastroschisis, duodenal atresia, pancreatic agenesis) |
|
Renal disease (renal agenesis) |
|
Neurofibromatosis |
|
Uterine-environmental factors |
|
Infection |
|
Cytomegalovirus |
|
Rubella |
|
Herpes, varicella |
|
Influenza |
|
Toxoplasmosis |
|
Oligohydramnios |
|
Placental abnormalities |
|
Placenta previa |
|
Abruptio placentae |
|
Placental malformation |
|
Multigestation |
|
Uterine anatomic abnormalities |
|
Maternal factors |
|
Prior IUGR infant |
|
Hypertension |
|
Diabetes (may also be associated with macrosomic infants) |
|
Nutritional deficits |
|
Gastrointestinal malabsorption |
|
Constitutional short stature |
|
Vascular disease |
|
Toxic exposures |
|
Smoking |
|
Alcohol |
|
Illicit drugs (heroin, cocaine) |
|
Prescription medications (folic acid antagonists, warfarin) |
|
Constitutional |
|
Constitutional short stature |
|
Female |
|
Birth order |
IUGR is defined as fetal weight below the tenth percentile and an abdominal girth below the 2.5 percentile for gestational age. As this definition implies, accurate fetal dating is critical to the diagnosis. At term, this corresponds to a birth weight of 2500 g (~5.5 lb). By this definition, approximately 5 % of all US infants demonstrate evidence of IUGR, accounting for approximately 175,000 infants annually in the United States.
Risk Factors
Factors associated with IUGR can be categorized into five categories: fetal genetic, uterine environmental, maternal, toxic exposures, and constitutional factors.
Fetal-Genetic Factors
A variety of genetic conditions are associated with restricted fetal growth and account for approximately 10 % of all cases. Early fetal growth is predominantly driven by growth in the number of fetal cells, cellular hyperplasia. This process is strongly influenced by genetic and fetal factors. As such early growth restriction is predominantly associated with fetal-genetic factors. Such conditions as Down syndrome (trisomy 21) and Turner’s syndrome are associated with an increased risk for IUGR. Structural growth defects such as anencephaly, achondroplasia, osteogenesis imperfecta, and renal and gastrointestinal (GI) defects are all associated with an increased risk of IUGR.
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