Small for gestational age embryos are those who are smaller in size than
normal for the gestational age, most commonly defined as a weight below the
10th percentile for the gestational age. Terminology
Not all fetuses that are SGA are pathologically growth restricted and, in
fact, may be constitutionally small. If small for gestational age babies have
been the subject of intrauterine growth restriction, formerly known as
intrauterine growth retardation, the term SGA associated with IUGR is used.
Intrauterine growth restriction refers to a condition in which a fetus is
unable to achieve its genetically determined potential size. This
functional definition seeks to identify a population of fetuses at risk for
modifiable but otherwise poor outcomes. This definition intentionally excludes
fetuses that are small for gestational age but are not pathologically
small.Infants born SGA with severe short stature are defined as having a length
less than 2.5 standard deviation scores below the mean.
A related term is low birth weight, defined as an infant with a birth weight
of less than 2500 g, regardless of gestational age at the time of birth.
Related definitions include very low birth weight which is less than 1500 g,
and extremely low birth weight which is less than 1000 g. Normal Weight at term
delivery is 2500 g - 4200 g. SGA is not a synonym of LBW, VLBW or
ELBW. Example: 35 week gestational age delivery, 2250g weight is appropriate
for gestational age but is still LBW. One third of low-birth-weight neonates -
infants weighing less than 2500g - are small for gestational age.
There is an 8.1% incidence of low birth weight in developed countries, and 6–30%
in developing countries. Much of this can be attributed to the health of the
mother during pregnancy. One third of babies born with a low birth weight are
also small for gestational age. Both low and high maternal serum Vitamin
D are associated with higher incidence SGA in white women, although the
correlation does not seem to hold for African American women.
Diagnosis The condition is determined by birth
weight and/or length. A related condition, IUGR, is generally
diagnosed by measuring the mother's uterus, with the fundal height being
less than it should be for that stage of the pregnancy. If it is suspected, the
mother will usually be sent for an ultrasound to confirm.
Causes Being small for gestational age is
broadly either: Being constitutionally small, wherein
the state is basically a genetic trait of the baby.
Intrauterine growth restriction, also called "pathological SGA"
= Intrauterine growth restriction= The risk factors for and etiologies of
pathological SGA can be broadly divided into 3 categories-
Fetal Maternal
Placental Management
90 percent of babies born SGA catch up in growth by the age of 2. However, all
SGA babies should be watched for signs of Failure-to-Thrive, hypoglycemia and
other conditions common to SGA babies. Hypoglycemia is common in asymmetrical
SGA babies because their larger brains burn calories at a faster rate than
their usually limited fat stores hold. Hypoglycemia is treated by frequent
feedings and/or additions of cornstarch-based products to the
feedings. For the 10 percent of those that are SGA
without catchup growth by the age of 2, an endocrinologist should be consulted.
Some cases warrant growth hormone therapy.
There are some common conditions and disorders found in many that are SGA.
They should be treated by the appropriate specialist:
Gastroenterologist - for gastrointestinal issues such as: reflux
and/or delayed gastric emptying Dietitian - to address caloric deficits.
Dietitians are usually brought in for cases that include FTT. Also, according
to the theory of thrifty phenotype, causes of growth restriction also
trigger epigenetic responses in the fetus that are otherwise activated in
times of chronic food shortage. If the offspring actually develops in an
environment rich in food it may be more prone to metabolic disorders, such as
obesity and type II diabetes. Speech Language Pathologist or
Occupational Therapist - for feeding issues. OTs may also treat sensory
issues Behaviorist - for feeding issues, a
behavioral approach may also be used, but usually for older children
Allergist - to diagnose or rule out food allergies
Ear, Nose and Throat doctor - to diagnose enlarged adenoids or tonsils
For IUGR, possible treatments include the early induction of labor, though
this is only done if the condition has been diagnosed and seen as a risk to the
health of the fetus. References