SGA: birth weight < 20th percentile for gestational age or < 2.5 kg.
LGA: birth weight > 90th percentile for gestational age or > 4 kg.
A: SGA: may be familial, constitutional, or due to IUGR.
IUGR is defined as either symmetrical or asymmetrical:
Asymmetrical IUGR: relative sparing of head circumference in relation to
weight and length:
. Due to impaired uteroplacental function 28 to maternal pre-eclampsia, DM
or nutritional deficiency during the 3rd trimester.
. Occurs when foetal growth rate in 3rd trimester exceeds maximal supply
from the placenta.
. There is preferential sparing of the cerebral perfusion at times of foetal
Symmetrical IUGR: head circumference, weight, and length are all proportionally affected to equivalent degrees:
. Indicative of a prolonged period of poor intrauterine growth.
. Caused by congenital intrauterine infections (TORCH) in the 1st trimester,
genetic factors such as single gene deletions and chromosomal disorders,
maternal smoking, drug and alcohol abuse, chronic medical conditions (e.g.
CRF), malnutrition, or multiple pregnancies.
LGA: macrosomia is a feature of infants of mothers with either gestational or
poorly controlled/undiagnosed DM.