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Corrected gestational age

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Here is a concise summary of Corrected Gestational Age (CGA) based on authoritative medical textbooks:

Corrected Gestational Age (CGA)

Definition

Corrected gestational age (also called corrected age, adjusted age, or postmenstrual age) accounts for prematurity when assessing a preterm infant's development.
There are two closely related terms:
TermFormulaWhen Used
Corrected ageChronologic age − number of weeks prematureDevelopmental assessment (infancy/toddlerhood)
Postmenstrual age (PMA)Gestational age at birth + chronologic age in weeksDuring hospitalization and perinatal period
"Until chronologic age 2 years, the development of a premature infant should be judged on corrected age (i.e., the chronologic age minus the number of weeks premature)." — Textbook of Family Medicine, 9e
"Postmenstrual age: Gestational age + chronologic age in weeks. Used in perinatal period during hospitalization and until 2 years of age." — The Harriet Lane Handbook, 23rd ed.

Why It Matters

Preterm infants have not completed the same neurodevelopmental maturation as term infants. Using chronologic age alone misclassifies many normal premature infants as developmentally delayed. CGA adjusts for this by "resetting" the developmental clock to the expected due date.

Clinical Applications

  1. Developmental milestone assessment — Motor, language, social, and cognitive milestones should be evaluated using corrected age up to 2 years of chronologic age.
  2. Retinopathy of prematurity (ROP) screening — Follow-up exams continue through at least term-corrected age, and timing thresholds use postmenstrual age (e.g., initial screen at 31 weeks PMA for infants born ≤27 weeks).
  3. Drug dosing in neonates — Many medications (e.g., aminoglycosides, acyclovir, oseltamivir) use postmenstrual age to determine appropriate dose intervals, as renal and hepatic maturation tracks with gestational rather than chronologic age.
  4. Anesthesia risk — Preterm infants younger than 50–60 weeks' postmenstrual age are at increased risk of postoperative apnea and generally require overnight monitoring after procedures.
  5. Infantile hemangioma (IH) risk stratification — Age thresholds for risk (e.g., < or ≥ 5 weeks) are based on corrected age for premature infants.

Example Calculation

A baby born at 30 weeks' gestation is now 4 months (16 weeks) old chronologically.
  • Postmenstrual age: 30 + 16 = 46 weeks PMA
  • Corrected age: 16 weeks − 10 weeks premature = 6 weeks corrected age
  • Developmental milestones should be assessed as if the baby is 6 weeks old, not 4 months.
Sources: The Harriet Lane Handbook 23rd ed.; Textbook of Family Medicine 9th ed.; Miller's Anesthesia 10th ed.; Wills Eye Manual
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