Small for Gestational Age (SGA) is a condition in which a developing fetus in the womb or an infant is smaller than normal for the baby’s gender and gestational age. Gestational age refers to the time period between conception and birth. It is typically measured in weeks and begins at the first day of the mother’s last menstrual cycle. SGA usually refers to a baby with a birthweight below the 10th percentile for babies of the same gestational age, meaning they are smaller than 90% of all babies of the same gestational age. SGA babies can either be proportionately small or have low weight and body mass, but normal length and size. SGA can be due to genetics or to fetal growth problems. SGA usually corresponds with intrauterine growth restriction, which occurs when the organs and tissues of the fetus cannot develop properly due to a lack of nutrients and oxygen. This condition can develop at any time during pregnancy and may be due to maternal disease, problems with the placenta, or chromosomal abnormalities. SGA may result in several problems at birth, including decreased oxygen levels, low Apgar scores, meconium aspiration, hypoglycemia, poor thermoregulation, and polycythemia, or too many red blood cells. SGA is typically diagnosed by ultrasound, Doppler flow, mother’s weight gain, and gestational assessment. Eating well and avoiding alcohol, drugs, and cigarettes may be helpful in preventing SGA.