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'Birth weight' is the weight of a baby at its birth. It has direct links with the gestational age at which the child was born and can be estimated during the pregnancy by measuring fundal height. A baby born within the normal range of weight for that gestational age is known as 'appropriate for gestational age' (AGA). Those born above or below that range have often had an unusual rate of development – this often indicates complications with the pregnancy that may affect the baby or its mother.
The incidence of birth weight being outside of the AGA is influenced by the parents in numerous ways, including:

★ Genetics

★ The health of the mother, particularly during the pregnancy

★ Environmental factors

★ Other factors, like multiple births, where each baby is likely to be outside the AGA, one more so than the other
There have been numerous studies that have attempted, with varying degrees of success, to show links between birth weight and later-life conditions, including diabetes, obesity, tobacco smoking and intelligence.

Contents

Large for gestational age

Diagnosis

Predetermining factors

Treatment

Small for gestational age

Diagnosis

Predetermining factors

Categories of growth restriction

Treatment

Influence on adult life

Obesity

Diabetes

Intelligence

Effects on the mother

See also

References

External links

Large for gestational age

'Large for gestational age' (LGA) babies are those whose birth weight lies above the 90th percentile for that gestational age. 'Macrosomia', also known as 'big baby syndrome', is sometimes used synonymously with LGA, or is otherwise defined as a fetus that weighs above 4000 grams (8 lb 13 oz) or 4500 grams (9 lb 15 oz) regardless of gestational age.

Diagnosis

LGA is generally not diagnosed until after the birth, as the size and weight of the child is rarely checked during the latter stages of pregnancy. Babies that are large for gestational age throughout the pregnancy can sometimes be seen during a routine ultrasound, although fetal weight estimations late in pregnancy are quite imprecise.[1]
There are believed to be links with ''polyhydramnios'' (excessive amniotic sac fluid).

Predetermining factors

One of the primary risk factors is poorly-controlled diabetes, particularly gestational diabetes (GD), as well as preexistent diabetes mellitus (DM). This increases maternal plasma glucose levels as well as insulin, stimulating fetal growth. The LGA newborn exposed to maternal DM usually has an increase only in weight. LGA newborns that have complications other than exposure to maternal DM present with universal measurements >90th percentile.
Other indicating factors include:

★ Gestational age; pregnancies that go beyond 40 weeks increase incidence

★ Fetal sex; male infants tend to weigh more than female infants

★ Genetic factors; taller, heavier parents tend to have larger babies, with an obese mother greatly increasing the chances

★ Excessive maternal weight gain

★ Multiparity (have 2-3x the number of LGA infants vs. primaparas)

★ Congenital anomalies (transposition of great vessels)

★ Erythroblastosis fetalis

★ Use of some antibiotics (amoxicillin, pivampcillin) during pregnancy
The condition is most common in mothers of African origin, partly due to the higher incidence of diabetes.

Treatment

Depending upon the relative size of the head of the baby and the pelvic diameter of the mother vaginal birth may become complicated. One of the most common complications is shoulder dystocia. Such pregnancies often end in caesarean sections in order to safely deliver the baby and to avoid birth canal lacerations. Upon birth, early feeding is essential to prevent fetal hypoglycemia. Early diagnosis of individual problems is required.

Small for gestational age

'Small for gestational age' (SGA) babies are those whose birth weight lies below the 10th percentile for that gestational age. They have usually been the subject of 'intrauterine growth restriction' (IUGR), formerly known as intrauterine growth retardation. 'Low birth weight' (LBW), is sometimes used synonymously with SGA, or is otherwise defined as a fetus that weighs less than 2500 g (5 lb 8 oz) regardless of gestational age. Other definitions include Very Low Birth Weight (VLBW) which is less than 1500 g, and Extremely Low Birth Weight (ELBW) which is less than 1000 g.
There is a 8.1% incidence of low birth weight in developed countries, and 6–30% in developing countries. Much of this can be attributed to the health of the mother during pregnancy. One third of babies born with a low birth weight are also small for gestational age.

Diagnosis

The condition is generally diagnosed by measuring the mother's uterus, with the fundal height being less than it should be for that stage of the pregnancy. If it is suspected, the mother will usually be sent for an ultrasound to confirm.

Predetermining factors

The risk factor/etiology can be broadly divided into 3 categories-

★ Fetal

★ Maternal

★ Placental
The primary risk factor is that development of the placenta is insufficient to meet the demands of the fetus, resulting in malnutrition of the developing fetus. There are numerous contributing factors, of both environmental and genetic origin:

★ Environmental factors such as poor nutrition, tobacco smoking, drug addiction or alcoholism

★ Severe anaemia (although hydrops may also occur)

★ Thrombophilia (tendency for thrombosis)

★ Prolonged pregnancy

★ Pre-eclampsia

★ Chromosomal abnormalities

★ Damaged or reduced placental tissue due to:

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★ Chronic renal failure

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★ Sickle cell anemia

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★ Phenylketonuria

★ Infections such as rubella, cytomegalovirus, toxoplasmosis or syphilis

★ Twins and multiple births.

Categories of growth restriction

There are two distinct categories of growth restriction, indicating the stage at which the development was slowed. Small for gestational age babies can be classified as having symmetrical or assymmetrical [asymmetrical] growth restriction.
'Symmetrical growth restriction', less commonly known as 'global growth restriction', 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. Common causes include:

★ Early intrauterine infections, such as cytomegalovirus, rubella or toxoplasmosis

★ Chromosomal abnormalities

★ Chronic high blood pressure

★ Severe malnutrition

★ Anemia

★ Maternal substance abuse (prenatal alcohol use can result in Fetal alcohol syndrome)
'Asymmetrical growth restriction' occurs when the embryo/fetus has grown normally for the first two trimesters but encounters difficulties in the third, usually pre-eclampsia. Such babies have a disparity in their length and head circumference when compared to the birth weight. A lack of subcutaneous fat leads to a thin and small body out of proportion with the head. Other symptoms include dry, peeling skin and an overly-thin umbilical cord, and the baby is at increased risk of hypoxia and hypoglycaemia.

Treatment

Possible treatments include the early induction of labour, though this is only done if the condition has been diagnosed and seen as a risk to the health of the fetus.

Influence on adult life

Studies have been conducted to investigate how a person's birth weight can influence aspects of their future life. This includes theorised links with obesity, diabetes and intelligence.

Obesity

A baby born small or large for gestational age (either of the two extremes) is thought to have an increased risk of obesity in later life. [2] [3] [4] [5] [6]

Diabetes

Babies that have a low birth weight are thought to have an increased risk of developing type 2 diabetes in later life. [7] [8] [9] [10]

Intelligence

Some studies have shown a direct link between an increased birth weight and an increased intelligence quotient. [11] [12] [13]

Effects on the mother

There is some evidence of a link between a child's birth weight and its mother's risk of cardiovascular disease. [14]

See also

★ MOMO syndrome

References

★ Mayes, M., Sweet, B. R. & Tiran, D. (1997). ''Mayes' Midwifery - A Textbook for Midwives'' 12th Edition, pp. 852–857. Baillière Tindall. ISBN 0-7020-1757-4

★ . Retrieved 30 May 2005.

External links

★ "Understanding IUGR A Parent's Guide"

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★ "Intrauterine Growth Restriction: Identification and Management" at the American Academy of Family Physicians (AAFP)

★ "Intrauterine growth restriction (IUGR)" at Health System, University of Virginia

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★ "Researchers link low birth weight to lower achievement"

★ "Management of Suspected Fetal Macrosomia"

★ "Vit D linked to baby birth weight" at BBC News, 25 April 2006

★ Born in Bradford - 2006 cohort study into the causes of low birth weight and infant mortality in Bradford, UK

★ Intrauterine Growth Restriction Help - IUGR factors and solutions

★ The IUGR prognostic scale