Classification of gestational age and birth weight

What it is

Birth weight and gestational age are two separate axes. By weight alone, low birth weight is a birth weight below 2.5 kg irrespective of the gestational age, very low birth weight is below 1.5 kg, and extremely low birth weight is below 1 kg. By weight against gestational age, appropriate for gestational age means the weight corresponds to the gestational age, and small for gestational age means the birth weight is below the expected for the gestational age; the same term is also defined as an estimated fetal weight below the 10th percentile for the appropriate gestational age. A small fetus is not always a growth restricted one. A constitutionally small fetus has a normal rate of growth and normal blood flow to the fetus, and is followed by repeating the US after 3 weeks. IUGR means the rate of growth is slowed, or that there is uteroplacental insufficiency. Gestational age has bands of its own, and they are asked by name. A term baby is born from 37 weeks to 41+6 weeks, and term itself divides into early term at 37-38 weeks and full term at 39-41 weeks. Preterm is born before 37 weeks and is then divided by how early: extremely preterm under 28 weeks, very preterm 28-31+6 weeks, moderate preterm 32-33+6 weeks, and late preterm 34-36+6 weeks, which is the last band before term. Post term is born at 42 weeks or more, so a baby born at 42 weeks is post term and not term.