What is the Difference Between Preterm and Small for Gestational Age?

The main difference between preterm and small for gestational age (SGA) lies in the definitions and the factors that contribute to each condition.

Preterm birth refers to the delivery of a baby before 37 weeks of gestational age. Preterm birth can lead to various health complications and developmental issues for the baby. Factors associated with preterm birth include younger maternal age, small stature, firstborns, and male sex of the baby.

Small for gestational age (SGA) is defined as a birth weight of less than the 10th percentile for gestational age. Smaller infants who are SGA may have normal birth weights but are still considered SGA due to factors such as weight, ethnicity, and parity. SGA infants are at an increased risk of perinatal mortality and morbidity.

In summary, preterm birth refers to the early delivery of a baby, while SGA refers to a baby's smaller size relative to its gestational age. Although both conditions can have long-term effects on the health of the baby, they are distinct from one another and are influenced by different factors.

On this page

What is the Difference Between Preterm and Small for Gestational Age?

Comparative Table: Preterm vs Small for Gestational Age

Preterm and small for gestational age (SGA) are two distinct concepts related to infant birth size and gestational age. Here is a table comparing the differences between the two:

Feature	Preterm	Small for Gestational Age (SGA)
Definition	Preterm birth is defined as a gestational age below 37 weeks.	SGA is often defined as a birth weight below the 10th percentile of the sex- and gestational age-specific standard.
Onset	Occurs prior to 37 weeks of gestation.	Can occur at any gestational age, but typically refers to infants born at term (37-41 weeks) who are smaller than expected for their gestational age.
Growth	Preterm infants may experience catch-up growth, especially if they are born near the threshold of viability (22-24 weeks).	SGA infants may experience catch-up growth, but this may be influenced by factors such as inadequate nutrition, feeding difficulties, and maternal socioeconomic status.
Risks	Preterm infants are at increased risk for various health issues, including respiratory distress syndrome (RDS) and mortality.	SGA infants are at increased risk for perinatal morbidity and mortality.
Prevalence	Preterm birth affects approximately 10% of all births worldwide.	The prevalence of SGA varies depending on the population and risk factors, but it is generally lower than that of preterm birth.

In summary, preterm birth refers to the early onset of labor, while SGA refers to an infant's birth weight being lower than expected for their gestational age. These two conditions can occur independently or in combination, and each has its own set of associated risks and potential complications.

Guilherme Mazui

Guilherme Mazui is graduated in journalism from the Federal University of Minas Gerais (UFMG) and a master's degree in Communication from the University of São Paulo (USP). In addition, he has experience in advertising writing and has worked as a content editor in several companies.