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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.
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.
The risk factor/etiology can be broadly divided into 3 categories-
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:
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 asymmetrical [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:
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.
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.
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Small_for_gestational_age". A list of authors is available in Wikipedia.|