Small for Gestational Age

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WHAT DOES THE TERM “SGA” (SMALL FOR GESTATIONAL AGE) MEAN?

SGA (small for gestational age) generally describes any infant whose birth weight and/or birth length was less than the 3rd percentile, adjusted for prematurity (gestational age). Between 3% and 10% of live births each year are diagnosed as SGA. In addition, when ultrasound evidence demonstrated poor fetal growth while in-utero, an infant may also be described as “IUGR”, which means the fetus experienced intrauterine growth restriction.

The factors behind why an infant is born SGA can be quite complex. The factors include fetal (such as genetic syndrome), maternal (such as substance use or infection), placental, and/or demographic (mother’s age, income level – these are both rare).

But setting aside these possible causes, 9 out of 10 infants born SGA do experience catch-up growth by the age of 2 years, and usually by 6 months of age. Catch-up growth typically means that the child’s length curve moves upward, crossing the 3rd percentile line at a minimum and ideally getting closer to the percentile curve the child should be at based on his or her parents. It is the smaller subset of SGA children, the 1 of 10 who fail to achieve catch-up growth by age 2, that are often referred to as “short SGA” and who are our focus.

This group of short SGA children typically include “idiopathic” SGA children – children who remain small for unknown reasons...parents who are of normal height, there is a history of non-smoking/non-drinking, and lab tests have ruled out known causative factors. It can be frustrating to be the parent of such an SGA child – you want answers to why your child isn’t growing. Here we hope to offer information on SGA children and to answer some of the possible questions you may have.

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