The growth of the fetus is usually proportional - there are precise tables available
from which it is possible to ascertain that the head circumference, the length of
the limbs, and the circumference of the abdomen concur with the gestational age.
There are many factors that can cause delay in intrauterine growth (intrauterine
growth retardation), of which some are genetic and some environmental. Usually,
but not always, growth retardation resulting from genetic causes will continue throughout
pregnancy and will be proportional. Disturbances of fetal blood flow mainly cause
delayed growth of the abdominal circumference and the length of the femur, signs
of which usually appear only in the second or third trimester.
The measurement of several parameters will establish the diagnosis. These include
the degree of growth retardation, the week of pregnancy in which it occurred, the
symmetry of the delay (are the head and limbs short to the same extent?) the blood
flow to the fetus, obstetric/placental causes that may explain the delay, intrauterine infection, other defects, etc.
Multidisciplinary counseling by a gynecologist from a high-risk pregnancy clinic,
an ultrasound specialist and a geneticist is required in order to evaluate the specific
cause for the delay in growth in each individual case. Based on the available data,
the degree and severity of the growth retardation, the week of gestation and other
parameters, the type of further follow-up/therapy will be determined. Whether amniocentesis
and other tests should be carried out will also be considered.
In cases of extreme intrauterine growth retardation, there will also be a delay
in the growth of the head circumference, and if this is severe, there may be significant
developmental implications, depending on the degree of delay.