INTRAUTERINE GROWTH RESTRICTION (IUGR)
INTRODUCTION
Intrauterine growth restriction (IUGR) is a term used to
describe a condition in which the fetus is smaller than expected for the number
of weeks of pregnancy. Another term for IUGR is fetal growth restriction.
Newborn babies with IUGR are often described as small for gestational age
(SGA).
A fetus with IUGR often has an estimated fetal weight less
than the 10th percentile. This means that the fetus weighs less than 90 percent
of all other fetuses of the same gestational age. A fetus with IUGR also may be
born at term (after 37 weeks of pregnancy) or prematurely (before 37 weeks).
Newborn
babies with IUGR often appear thin, pale, and have loose, dry skin. The
umbilical cord is often thin and dull-looking rather than shiny and fat. Babies
with IUGR sometimes have a wide-eyed look. Some babies do not have this
malnourished appearance but are small all-over.
CAUSES
OF IUGR
Intrauterine growth restriction results when a problem or
abnormality prevents cells and tissues from growing or causes cells to decrease
in size. This may occur when the fetus does not receive the necessary nutrients
and oxygen needed for growth and development of organs and tissues, or because
of infection. Although some babies are small because of genetics most IUGR is
due to other causes. Some factors that may contribute to IUGR include the
following:
Maternal factors:
§
high blood pressure
§
chronic kidney disease
§
advanced diabetes
§
heart or respiratory
disease
§
malnutrition, anemia
§
infection
§
substance abuse
(alcohol, drugs)
§
cigarette smoking
Utero placental factors :
§ decreased blood flow in the uterus and placenta
§ placental abruption (placenta detaches from the uterus)
§ placenta previa (placenta attaches low in the uterus)
§ infection in the tissues around the fetus
Fetal factors:
§
multiple gestation (twins, triplets, etc.)
§ infection
§ birth defects
§ chromosomal abnormality
COMPLICATIONS OF IUGR
IUGR can begin at any time in pregnancy. Early-onset IUGR
is often due to chromosomal abnormalities, maternal disease, or severe problems
with the placenta. Late-onset growth restriction (after 32 weeks) is usually
related to other problems.
With IUGR, the growth of the baby's overall body and organs
are limited, and tissue and organ cells may not grow as large or as numerous.
When there is not enough blood flow through the placenta, the fetus may only receive
low amounts of oxygen. This can cause the fetal heart rate to decrease placing
the baby at great risk.
Babies with IUGR may have problems at birth including:
§
decreased oxygen
levels
§
low Apgar scores
§
meconium aspiration
(inhalation of the first stools passed in utero), which can lead to difficulty
breathing
§
hypoglycemia
§
difficulty maintaining
normal body temperature
§
polycythemia
(increased red blood cells)
Severe IUGR may result in stillbirth. It may also lead to
long-term growth problems in babies and children.
Intrapartum
Asphyxia
Because the fetus is compromised
with IUGR, its ability to tolerate the stress of labor is decreased. Therefore,
when uterine contractions occur and the flow of blood to the fetus is
diminished with each contraction, the fetus with IUGR may not be able to adapt.
This leads to an imbalance between the ability of the placenta to supply the
fetus with oxygen and nutrients and the need for these substances. When an
imbalance occurs, this may lead to an accumulation of byproducts resulting in
acidosis which can be harmful. If intrapartum asphyxia is allowed to progress,
irreversible brain damage can occur.
Neonatal Hypoglycemia and Hypocalcemia
As the result of IUGR, a newborn
may be deficient in glucose (sugar) and calcium. The lack of these important
substances can result in significant compromise to the newborn and result in
neurological damage.
Meconium Aspiration
This occurs when the fetus
defecates in the uterus resulting in the appearance of a brown, murky substance.
Meconium aspiration is of major concern. In severe forms, the newborn may
develop lung disease resulting in respiratory and cardiovascular complications
that could lead to neonatal death.
Neurodevelopmental Delay
A number of studies have shown that fetuses with
significant IUGR are at higher risk for developmental delays, cardiovascular
disease, and other problems later in life. For these reasons, and those stated
above, it is important to identify the fetus with IUGR and manage the pregnancy
accordingly
DIAGNOSIS OF IUGR
§
Fundal Height
The height of the fundus can be measured from the pubic
bone. This measurement in centimeters usually corresponds with the number of
weeks of pregnancy after the 20th week. If the measurement is low for the
number of weeks, the baby may be smaller than expected.
§
Ultrasound
Ultrasound is a more accurate method of estimating fetal size. Measurements
include the diameter of the head (Biparietal Diameter or BPD), the
circumference of the head, the circumference of the abdomen, and the length of
the femur bone of the leg. The fetal abdominal
circumference is a helpful indicator of fetal nutrition.
§
Doppler flow
Another way to interpret and diagnose IUGR during pregnancy
is Doppler flow, which use sound waves to measure blood flow. The sound of
moving blood produces wave-forms that reflect the speed and amount of the blood
as it moves through a blood vessel. Blood vessels in the fetal brain and the
umbilical cord blood flow can be checked with Doppler flow studies.
§
Mother's weight
gain
A
mother's weight gain can also indicate a baby's size. Small maternal weight
gains in pregnancy may correspond with a small baby.
MANAGEMENT OF IUGR
Management of IUGR depends on the severity of growth
restriction, and how early the problem began in the pregnancy. Generally, the
earlier and more severe the growth restriction, the greater the risks to the
fetus. Careful monitoring of a fetus with IUGR and ongoing testing may be
needed.
Some of the ways to watch for potential problems include
the following:
§
Fetal movement
counting - keeping track of fetal kicks
and movements. A change in the number or frequency may mean the fetus is under
stress.
§
Non Stress Testing - a test that watches the fetal heart rate for increases
with fetal movements, a sign of fetal well-being.
§
Biophysical profile - a test that combines the non stress test with an
ultrasound to evaluate fetal well-being.
§
Ultrasound - Ultrasounds are used to view internal organs as they
function, and to assess blood flow through various vessels. Ultrasounds are
used to follow fetal growth.
§
Doppler flow
studies - a type of ultrasound which use
sound waves to measure blood flow.
TREATMENT OF IUGR
Although it is not possible to reverse IUGR, some
treatments may help slow or minimize the effects. Management will be determined
based on:
§
Maternal and fetal
overall health, and medical history
§
the extent of the
condition
§
tolerance for specific
medications, procedures
Nutrition
Some studies have shown that increasing
maternal nutrition may increase gestational weight gain and fetal growth.
Bedrest
Bedrest in the hospital or at home may
help improve circulation to the fetus.
Delivery
If IUGR endangers the health of the fetus,
then an early delivery may be necessary.
PREVENTION
Intrauterine growth restriction may occur, even when the
mother is in good health. However, some factors may increase the risks of IUGR,
such as cigarette smoking and poor maternal nutrition. Avoiding harmful
lifestyles, eating a healthy diet, and getting prenatal care may help decrease
the risks for IUGR. Early detection may also help with IUGR treatment and
outcome.
