Terminology		The AAP has issued guidelines on preferred terminology during the perinatal period which this lecture will follow. Gestational age (GA) is the time from the first day of the mother's last menstrual period (LMP) to the day of delivery. Although "menstrual age" means the same, GA is the preferred term. By convention, it is expressed as completed weeks and days and can be rounded down, but not up. That is, a baby with a GA of 31 weeks, 5 days is referred to as a 31-weeker, not a 32-weeker. Chronologic age (CA) is the time elapsed, in completed weeks and days, since birth. Postmenstrual age (PMA) is the GA plus the CA. A baby born at 31 weeks, 5 days, who is now 29 days old, has a PMA of 35 weeks, 6 days. Conceptional age or postconceptional age (PCA) is the time from the day of conception to the day of delivery. This is usually 2 weeks shorter than GA. Even in cases where assisted reproductive technology has allowed precise determination of the date of conception, GA should be used instead of PCA to avoid confusion. For example, a premie conceived via this technology and born with a PCA of 25 weeks, has a GA of 27 weeks. Outcomes for this baby should be compared to those of 27-weekers, not 25. Corrected age is derived by subtracting the number of weeks born before the due date (EDC) from the CA. This "correction" for the degree of prematurity is used until 3 years (CA) in preterms. The term "corrected age" should be used instead of "corrected GA" or "adjusted age". During the perinatal period and the NICU hospital stay, PMA should be used. After discharge from the NICU, corrected age should be used. After the CA of 3 years, CA should be used. Finally, postconceptual age refers to the elapsed time from the day the parents first entertained the "concept" of having a child. While this may be of sentimental interest to them, it is medically irrelevant and the term should not be used. Return to top of page