Clinical Topic
Growth in Babies Born Small for Gestational Age:
A Guide for Families
What Does Small for Gestational Age (SGA) Mean?
Small for gestational age (SGA) refers to a baby who is born with a weight below the 10th percentile on the growth chart for gestational age and sex. Having a weight below the 10th percentile means that 90 out of every 100 babies of the same age and sex weigh more at birth.
What is a Growth Chart?
A growth chart uses lines to display an average growth path for a baby of a certain age, sex, length, and weight. Each line indicates a certain percentage of the population who would be that particular length or weight at a particular age. If a boy’s length is plotted on the 25th percentile line, for example, this indicates that approximately 25 out of 100 boys his age are shorter than him. Babies often do not follow these lines exactly, but most often, their growth plots are roughly parallel to these lines. A baby who has a length plotted below the third percentile line (some use the fifth percentile line as a cutoff) is considered to be short for age compared with the general population. The growth charts can be found on the Centers for Disease Control and Prevention Web site at https://www.cdc.gov/growthcharts/data/set1clinical/set1bw.pdf.
What Does Being Born SGA Mean for Your Baby’s Growth in the Future?
Most babies who are born SGA will grow well enough for their length and/or weight to reach a normal point on the growth curve by 2 to 4 years of age. Babies born SGA whose height remains 2 standard deviations below what is typical by age 2 to 4 years may be shorter as adults than would be expected relative to their families.
What Causes Babies To Be Born SGA?
Usually, the reason is not known. Sometimes, it could be because of fetal growth restriction (FGR) or intrauterine growth restriction (IUGR), which means that the baby did not grow well while in the mother’s womb. Some of the known risk factors for babies being born SGA or with FGR/IUGR include:
- Maternal smoking
- Poor nutrition
- Preeclampsia or eclampsia
- Placenta problems
- Pregnant with multiple infants, such as twins or triplets
- Genetic problems
- Infections during pregnancy, such as rubella, toxoplasmosis, cytomegalovirus, or syphilis
- Maternal alcohol or drug use
Other times, being born SGA could be the result of factors such as maternal height, weight, and ethnicity, as well as multiple infants.
What Tests Might Be Used To Assess Your Baby?
The best “test” is to monitor your baby’s growth over time using the growth chart. The time frame is typically 2 to 6 months, depending on the age of the baby. Babies who are born SGA or with FGR/IUGR often grow well and do not usually need any special tests or treatments to help them grow. If there is a growth concern, the doctor may check your child’s bone age (radiograph of left hand and wrist) or perform blood tests to look for problems that could be affecting growth. Growth hormone may occasionally be considered for use in children born SGA whose height remains 2 standard deviations below what is normal for their age and sex between 2 and 4 years of age.
Pediatric Endocrine Society/American Academy of Pediatrics Section on Endocrinology Patient Education Committee
Copyright © 2018 American Academy of Pediatrics and Pediatric Endocrine Society. All rights reserved. The information contained in this publication should not be used as a substitute for the medical care and advice of your pediatrician. There may be variations in treatment that your pediatrician may recommend based on individual facts and circumstances.