science

Intrauterine growth restriction

Intrauterine growth restriction is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Intrauterine growth restriction rather than just read about it. In short: Intrauterine growth restriction (IUGR), or fetal growth restriction, is the poor growth of a fetus while in the womb during pregnancy. IUGR is defined by clinical features of malnutrition and evidence of reduced growth regardless of an infant's birth weight percentile.

Key takeaways

Intrauterine growth restriction belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Intrauterine growth restriction to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Intrauterine growth restriction from memory before moving on to harder problems.

Reference excerpt

Intrauterine growth restriction (IUGR), or fetal growth restriction, is the poor growth of a fetus while in the womb during pregnancy. IUGR is defined by clinical features of malnutrition and evidence of reduced growth regardless of an infant's birth weight percentile. The causes of IUGR are broad and may involve maternal, fetal, or placental complications. At least 60% of the 4 million neonatal deaths that occur worldwide every year are associated with low birth weight, caused by intrauterine growth restriction (IUGR), preterm delivery, and genetic abnormalities, demonstrating that under-nutrition is already a leading health problem at birth. Intrauterine growth restriction can result in a baby being small for gestational age (SGA), which is most commonly defined as a weight below the 10th percentile for the gestational age. At the end of pregnancy, it can result in a low birth weight.

Types There are two major categories of IUGR: pseudo IUGR and true IUGR With pseudo IUGR, the fetus has a birth weight below the tenth percentile for the corresponding gestational age but has a normal ponderal index, subcutaneous fat deposition, and body proportion. Pseudo IUGR occurs due to uneventful intrauterine course and can be rectified by proper postnatal care and nutrition. Such babies are also called small for gestational age. True IUGR occurs due to pathological conditions which may be either fetal or maternal in origin. In addition to low body weight they have abnormal ponderal index, body disproportion, and low subcutaneous fat deposition. There are two types – symmetrical and asymmetrical. Some conditions are associated with both symmetrical and asymmetrical growth restriction.

Asymmetrical Asymmetrical IUGR accounts for 70-80% of all IUGR cases. In asymmetrical IUGR, there is decreased oxygen or nutrient supply to the fetus during the third trimester of pregnancy due to placental insufficiency. This type of IUGR is sometimes called "head sparing" because brain growth is typically less affected, resulting in a relatively normal head circumference in these children. Because of decreased oxygen supply to the fetus, blood is diverted to the vital organs, such as the brain and heart. As a result, blood flow to other organs – including liver, muscle, and fat – is decreased. This causes abdominal circumference in these children to be decreased. A lack of subcutaneous fat leads to a thin and small body out of proportion with the liver. Normally at birth the brain of the fetus is 3 times the weight of its liver. In IUGR, it becomes 5-6 times. In these cases, the embryo/fetus has grown normally for the first two trimesters but encounters difficulties in the third, sometimes secondary to complications such as pre-eclampsia. Other symptoms than the disproportion include dry, peeling skin and an overly-thin umbilical cord. The baby is at increased risk of hypoxia and hypoglycemia. This type of IUGR is most commonly caused by extrinsic factors that affect the fetus at later gestational ages. Specific causes include:

Chronic high blood pressure Severe malnutrition Genetic mutations, Ehlers–Danlos syndrome

Symmetrical Symmetrical IUGR is commonly known as global growth restriction, and indicates that the fetus has developed slowly throughout the duration of the pregnancy and was thus affected from a very early stage. The head circumference of such a newborn is in proportion to the rest of the body. Since most neurons are developed by the 18th week of gestation, the fetus with symmetrical IUGR is more likely to have permanent neurological sequelae. Common causes include:

Early intrauterine infections, such as cytomegalovirus, rubella or toxoplasmosis Chromosomal abnormalities Anemia Maternal substance use (prenatal alcohol use can result in Fetal alcohol syndrome)

Causes IUGR is caused by a variety of factors; these can be fetal, maternal, placental or genetic factors.

Maternal Pre-pregnancy weight and nutritional status Poor weight gain during pregnancy Malnutrition Anemia Substance use: smoking, alcohol, drugs including marijuana or cocaine Medication: warfarin, steroids, anticonvulsants Inter-pregnancy interval of less than 6 months Assisted reproductive technologies Pre-gestational diabetes Gestational diabetes Pulmonary disease Cardiovascular disease Kidney disease Hypertension Celiac disease increases the risk of intrauterine growth restriction by an odds ratio of approximately 2.48 Subclinical hypothyroidism Blood clotting disorder/disease (e.g., Factor V Leiden)

Uteroplacental Preeclampsia Multiple gestation Uterine malformations Placental insufficiency

Fetal Chromosomal abnormalities Vertically transmitted infections: TORCH, Malaria, congenital HIV infection, Syphilis Erythroblastosis fetalis Congenital abnormalities

Genetic Placental genes Maternal genes: Endothelin-1 over-expression, Leptin under-expression Fetal genes

Pathophysiology If the cause of IUGR is extrinsic to the fetus (parental or uteroplacental), transfer of oxygen and nutrients to the fetus is decreased. This causes a reduction in the fetus' stores of glycogen and lipids. This often leads to hypoglycemia at birth. Polycythemia can occur secondary to increased erythropoietin production caused by the chronic hypoxemia. Hypothermia, thrombocytopenia, leukopenia, hypocalcemia, and bleeding in the lungs are often results of IUGR. Infants with IUGR are at increased risk of perinatal asphyxia due to chronic hypoxia, usually associated with placental insufficiency, placental abruption, or an umbilical cord accident. This chronic hypoxia also places IUGR infants at elevated risk of persistent pulmonary hypertension of the newborn, which can impair an infant's blood oxygenation and transition to postnatal circulation. If the cause of IUGR is intrinsic to the fetus, growth is restricted due to genetic factors or as a sequela of infection. IUGR is associated with a wide range of short- and long-term neurodevelopmental disorders.

… excerpt ends here. Continue reading the full article.

Illustrations

Worked examples

Example 1 — a first encounter with Intrauterine growth restriction

Start with the simplest possible case. Write down what Intrauterine growth restriction claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Intrauterine growth restriction before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Intrauterine growth restriction ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Intrauterine growth restriction

In research: Intrauterine growth restriction appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Intrauterine growth restriction in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Intrauterine growth restriction is common in secondary-school and first-year university syllabi. It links to neighbouring topics Disorders related to length of gestation and fetal growth, Embryology, Human pregnancy, so understanding it makes those chapters shorter.
In everyday life: Look for Intrauterine growth restriction outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Intrauterine growth restriction in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Intrauterine growth restriction means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Intrauterine growth restriction out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Intrauterine growth restriction in simple terms?

Why does Intrauterine growth restriction matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Intrauterine growth restriction?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Intrauterine growth restriction.