Intrauterine growth restriction (IUGR) refers to a fetal birth weight below the 10th percentile or two standard deviations below the average weight for gestational age. If gestational age reaches 37 weeks and the newborn weighs less than 2.5 kilograms, it is also termed fetal intrauterine growth deficiency. Medically defined, IUGR occurs when a fetus's weight is less than 10% of the normal range for its gestational age. Conversely, 10% of fetuses at the same gestational age are considered overweight.Historically, the term "retardation" was used to describe fetal growth restriction, but this word does not encompass brain development issues. The American College of Obstetricians and Gynecologists decided to replace this term with "restriction" to accurately reflect the fetus's condition. Today, fetal growth restriction has become the standard terminology.
The causes of fetal growth restriction are complex.Generally, causes fall into two main categories. The first involves issues with the child itself, such as abnormalities. The second relates to placental blood supply. If the mother suffers from heart disease, hypertension, diabetes, nephritis, or similar conditions, these can affect placental blood flow and consequently impact fetal development. Therefore, couples planning to conceive should undergo various medical examinations at the hospital six months in advance. Women with the aforementioned conditions should receive adequate treatment and consider pregnancy only after their condition has improved.
Symptoms and Signs of Fetal Intrauterine Growth Restriction:
1. Intrauterine Growth Restriction with Symmetrical Growth
This is a primary form of intrauterine growth restriction, where growth-inhibiting factors are present at conception or early pregnancy, causing internal fetal abnormalities or stemming from genetic factors.
Characteristics: Weight, length, and head circumference are proportionate but below the normal range for gestational age.No signs of malnutrition are visible externally. Organ differentiation or maturity corresponds to gestational age, but the number of cells in each organ is reduced, and brain weight is low. The placenta is small with fewer cells. The fetus shows no signs of hypoxia. Half of these fetuses have congenital malformations, with a poor prognosis. Postnatally, the newborn may exhibit brain nerve developmental disorders accompanied by intellectual disability in childhood.
2. Exogenous Asymmetric Fetal Growth Restriction
This represents secondary growth impairment where embryonic development is normal in early pregnancy but is compromised by adverse factors in late gestation. Examples include complications such as preeclampsia, hypertension, diabetes, or post-term pregnancy, leading to placental insufficiency.
Characteristics: Neonates exhibit disproportionate growth with length and head circumference corresponding to gestational age but low birth weight. Appearance may resemble malnutrition or postmaturity. Organ cell counts are normal but cell volumes are reduced, most notably in the liver. Placental volume is normal but often shows infarcts, calcifications, or membrane hyperpigmentation. Neonates frequently present with hypoglycemia at birth.
3. Exogenous Symmetrical Fetal Growth Restriction: A combination of the above two types, often resulting from maternal and fetal factors, folate deficiency, amino acid deficiency, trace element deficiency, or exposure to harmful drugs. Although the causative factors are external, their effects occur throughout the entire pregnancy.
Characteristics: Proportional body length, weight, and head circumference, though all measurements are small. External signs of malnutrition are present. All organ volumes are reduced. The placenta is small but appears normal externally. Intrauterine hypoxia is uncommon, but metabolic dysfunction is present. Reduced brain cell count is observed in 60% of cases. Newborns often exhibit significant growth and intellectual impairments.
Fetuses with intrauterine growth restriction (IUGR) often appear thin, pale, and have loose, dry skin at birth. The umbilical cord is thinner and duller, lacking the normal luster and fullness. Some IUGR newborns have wide-set eyes, while others may not appear malnourished but simply have a smaller overall body size. However, it's important to note that small size alone does not necessarily indicate IUGR, just as increased size and weight gain do not always signify a large fetus.In reality, few obvious symptoms indicate a fetus is smaller than expected. Typically, routine examinations and abdominal palpation by healthcare professionals only suggest the uterus or fetus appears smaller than the gestational age. Diagnosis requires ultrasound or other specialized testing.