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Intrauterine growth restriction (IUGR) refers to poor growth of a fetus while in the mother's womb during pregnancy. The causes can be many, but most often involve poor maternal nutrition or lack of adequate oxygen supply to the fetus. At least 60% of the 4 million neonatal deaths that occur worldwide every year are associated with low birth weight (LBW), caused by intrauterine growth restriction (IUGR), preterm delivery, and genetic/chromosomal abnormalities, demonstrating that under-nutrition is already a leading health problem at birth. Intrauterine growth restriction can result in baby being Small for Gestational Age (SGA), which is most commonly defined as a weight below the 10th percentile for the gestational age.〔(Small for gestational age (SGA) ) at MedlinePlus. Update Date: 8/4/2009. Updated by: Linda J. Vorvick. Also reviewed by David Zieve.〕 At the end of pregnancy, it can result in a low birth weight. ==Symmetrical vs. asymmetrical== There are 2 major categories of IUGR: symmetrical and asymmetrical.〔(【引用サイトリンク】title=Intrauterine Growth Restriction: Identification and Management - August 1998 - American Academy of Family Physicians )〕 Some conditions are associated with both symmetrical and asymmetrical growth restriction. ''Asymmetrical IUGR'' is more common (70%). In asymmetrical IUGR, there is restriction of weight followed by length. The head continues to grow at normal or near-normal rates (head sparing). A lack of subcutaneous fat leads to a thin and small body out of proportion with the head. This is a protective mechanism that may have evolved to promote brain development. 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 hypoglycaemia. 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 IUGR'' is less common (20-25%). It 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 sequela. Common causes include: *Early intrauterine infections, such as cytomegalovirus, rubella or toxoplasmosis *Chromosomal abnormalities *Anemia *Maternal substance abuse (prenatal alcohol use can result in Fetal alcohol syndrome) 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「intrauterine growth restriction」の詳細全文を読む スポンサード リンク
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