Babies come in all sizes. Some are just naturally larger or smaller than others.
But in certain cases, babies in the womb are smaller than they should be. When
this happens, it is called intrauterine growth restriction, or IUGR.
About IUGR
IUGR is when a baby in the womb fails to grow at the expected rate during
the pregnancy. In other words, at any point in the pregnancy, the baby is not as big
as would be expected for how far along the mother is in her pregnancy (this timing
is referred to as an unborn baby's "gestational age").
Babies who have IUGR often have a low weight at birth. If the weight is below the
10th percentile for a baby's gestational age (meaning that 90% of babies that age
weigh more) the baby is also referred to as "small for gestational age," or SGA.
It's important to note that not all babies who are small for gestational age had
IUGR while in the womb. For example, some are healthy babies who are just born smaller
than average because their parents are small in stature.
The two types of IUGR are:
- Symmetrical IUGR, in which a baby's body is proportionally small
(meaning all parts of the baby's body are similarly small in size).
- Asymmetrical IUGR, which is when the baby has a normal-size head
and brain but the rest of the body is small.
Causes
In many cases, IUGR is the result of a problem that prevents a baby from getting
enough oxygen and nutrients. This lack of nourishment slows the baby's growth.
It can happen for a number of reasons. A common cause is placental insufficiency,
in which the tissue that delivers oxygen and nutrients to the baby is not attached
properly or isn't working correctly.
Other possible causes during a woman's pregnancy include:
Risk Factors
IUGR is more likely to occur in women who are carrying more than one baby or who
had a previous baby who was SGA or had IUGR. Certain medical conditions, such as some
types of heart, lung, blood, or autoimmune disease, and anemia also can increase a
woman's risk of developing IUGR. So can eating poorly or being underweight before
or during pregnancy.
Diagnosis
Since not all babies who are small have IUGR, an accurate diagnosis is important.
This starts with correctly determining the baby's gestational age by accurately dating
the pregnancy.
At first, gestational age is estimated using the first day of a woman's last menstrual
period. Later in the pregnancy (usually between weeks 8 and 13), it is confirmed through
an ultrasound. Once a baby's gestational age is known, doctors use it to watch the
baby's growth and compare it with the expected growth rate. If the baby is growing
more slowly than expected (sometimes referred to as "small for dates"), doctors will
continue to watch the baby's growth and may do more tests to see whether the baby
has IUGR.
Watching growth is done in several ways. A measurement called the uterine
fundal height helps estimate a baby's size by measuring a mother's belly
from the top of the pubic bone to the top of the uterus.
Another way is to use ultrasounds. In fact, IUGR is usually
diagnosed through an ultrasound examination.
During an ultrasound, a technician coats the woman's belly with a gel and then
moves a probe (wand-like instrument) over it. High-frequency sound waves "echo" off
the body and create pictures of the baby on a computer screen. These pictures can
be used to estimate the baby's size and weight.
Although these estimates might not be exact, they help health care providers track
the baby's growth and see if there's a problem. Ultrasounds also can help identify
other issues, such as problems with the placenta or low amniotic fluid levels.
Health care providers also might do other tests if they believe a baby has IUGR,
such as:
- fetal monitoring to track the baby's heart rate and movements
- screenings for infections
- amniocentesis
to help find the cause of IUGR (and sometimes to help determine lung maturity and
whether the baby is likely to be able to breathe on his or her own)
If a Baby has IUGR
When IUGR is diagnosed, treatment is decided based on the baby's condition and
the woman's month of pregnancy. The baby will be closely watched (usually with frequent
prenatal visits and ultrasounds) to keep track of growth and watch for other potential
problems.
Treatment also might include managing any maternal illness and ensuring that
the mother eats a healthy and nutritious diet and gains the appropriate amount of
weight. Some women are placed on bed rest to try to improve blood flow to the baby.
In some cases, health care providers will recommend inducing labor and delivery
early if monitoring shows that a baby has stopped growing or has other problems. Although
early delivery might be necessary, the goal is to keep the baby safe in the womb for
as long as possible.
A cesarean section
(C-section) might be done if the stress of a vaginal delivery is considered too
risky for the baby.
Outlook
Unfortunately, babies with IUGR are more likely to have health problems both before
and after birth. Those who are born
prematurely or are very small at birth are more likely to have problems that result
in longer hospital stays. They also might need special care after birth, such as help
breathing or medicine to prevent infections.
Other problems that can be related to IUGR include:
- increased likelihood of C-section delivery
- problems with breathing and feeding
- trouble maintaining body temperature
- abnormal blood cell counts
- low blood sugar level (hypoglycemia)
- decreased ability to fight infection
- neurological problems
- increased likelihood of stillbirth (dying in the womb before birth)
The long-term effects of IUGR may depend on the condition that caused the problem
in the first place.
Coping
When a woman learns that her baby has or might have IUGR, the best thing she can
do is to keep all of her prenatal visits and testing appointments and follow her health
care provider's recommendations. She also should take care of herself by eating
a healthy diet; getting
enough sleep; and avoiding alcohol, drugs, and tobacco.
