Definition

Small for gestational age means that a fetus or an infant is smaller or less developed than normal for the baby's sex and gestational age. Gestational age is the age of a fetus or baby that starts on the first day of the mother's last menstrual period.

Alternative Names

Low birth weight

Information

Ultrasound is used to find out if a fetus is smaller than normal for their age. This condition is called intrauterine growth restriction. The most common definition of small for gestational age (SGA) is a birth weight that is below the 10th percentile. At the time of the ultrasound exam, your health care provider may use other findings, such as the amount of amniotic fluid surrounding the baby, to further understand the baby's condition.

Causes for SGA fetus may include:

• Genetic diseases
• Inherited metabolic diseases
• Chromosome anomalies
• Multiple gestations (twins, triplets, and more)
• Abnormal placenta
• High blood pressure

A developing baby with intrauterine growth restriction will be small in size and can have problems such as:

• Increased red blood cells
• Low blood sugar
• Low body temperature

References

Baschat AA, Galan HL. Intrauterine growth restriction. In: Landon MB, Galan HL, Jauniaux ERM, et al, eds. Gabbe's Obstetrics Essentials: Normal and Problem Pregnancies. 8th ed. Philadelphia, PA: Elsevier; 2019:chap 33.

Suhrie KR, Tabbah SM. High-risk pregnancies. In: Kliegman RM, St. Geme JW, Blum NJ, Shah SS, Tasker RC, Wilson KM, eds. Nelson Textbook of Pediatrics. 21st ed. Philadelphia, PA: Elsevier; 2020:chap 114.