Gestational Age and Birthweight Classification

Gestational Age and Birthweight Classification

1. Gestational Age and Birthweight Classification

2. Gestation is the period of fetal development from the time of conception to birth. Gestational age (or menstrual age), as defined by the American Academy of Pediatrics (AAP), is the “time elapsed between the first day of the last menstrual period (LMP) and the day of delivery It is expressed in completed weeks

3. Gestational age and birthweight classification help the neonatologist to categorize infants, guide treatment, and assess risks for morbidity and mortality

4. Neonates can be classified based on gestational age (preterm, late preterm, early term, full or late term, post term) birthweight ( eg , extremely low birthweight , very low birthweight , low birthweight ) gestational age and birthweight combined (small for gestational age [SGA], appropriate for gestational age [AGA], large for gestational age [LGA]). The AAP recommends that all newborns be classified by birthweight and gestational age.

5. Newborn classification based on gestational age Extremely preterm: <28 weeks Very preterm: 28 0/7 to 31 6/7weeks Moderately preterm: 32 0/7 to 33 6/7 weeks Preterm <37 weeks Early term 37 0/7 to 38 6/7 weeks Full term 39 0/7 to 40 6/7 weeks Late term 41 0/7 to 41 6/7 weeks Post term 42 0/7 weeks or more

6. Birthweight classification A. Micro preemie <800 g. B. Extremely low birthweight (ELBW)<1000g. Very low birthweight (VLBW) <1500g. Low birthweight (LBW)<2500. Normal birthweight (NBW) 2500-4000 High birthweight (HBW)>4000g

7. Classification by birthweight and gestational age combined. SGA (small for gestational age) AGA (appropriate for gestational age) LGA (large for gestational age).

8. Appropriate for gestational age (AGA) Defined as a birthweight between the 10th and 90th percentiles for the infant’s gestational age.

9. Small for gestational age (SGA). Defined as birthweight 2 standard deviations below the mean weight for gestational age or below the 10th percentile for gestational age. SGA refers to the size of the infant at birth and not fetal growth.

10. SGA **maternal factors ( eg , chronic disease, malnutrition, multiple gestation, high altitude, or conditions affecting the blood flow and oxygenation in the placenta [hypertension, preeclampsia, smoking]) **placental factors ( eg , infarction, previa , abruption, anatomic malformations), **fetal factors (usually symmetric; birthweight , length, and head circumference all depressed the same) congenital infections ( eg , TORCH [toxoplasmosis, other, rubella, cytomegalovirus, herpes simplex virus] chromosomal abnormalities congenital malformations ( eg , dysmorphic syndromes and other congenital anomalies, fetal diabetes mellitus, familial causes, multiple gestation, constitutional).

11. Large for gestational age (LGA) infants of diabetic mothers (maternal or gestational ) infants with Beckwith- Wiedemann syndrome or other syndromes constitutionally large infants with large parents, postmature infants (gestational age >42 weeks) infants with hydrops fetalis .

12. Other age terminology Chronologic age (or postnatal age): The time elapsed since birth expressed in days, weeks, months, or years. Corrected age (or adjusted age; only used in children born preterm <3 years) Corrected age is the chronologic age minus the number of weeks born before 40 weeks’ gestation and is the preferred term to describe the age of preterm infants after the perinatal period. It is expressed in weeks or months.