Since
the NICHD was founded, one of its main focuses has been on
understanding the causes of birth defects, and on their treatments and
prevention. The March of Dimes Birth Defects Foundation
defines "birth defects" as: an abnormality of structure, function, or
metabolism (body chemistry) present at birth that results in physical
or mental disability, or is fatal. To date, researchers have identified
thousands of different birth defects. Currently, birth defects rank as
the leading cause of death for infants during the first year of life.
Birth defects can be caused by different factors, such as:
- Genetic problems that result from the failure of one or more genes to work properly
- Problems with the number or structure of chromosomes, such as extra or missing groups of genes
- Things
that happen to a woman during pregnancy, such as getting rubella or
German measles while pregnant, having untreated or uncontrolled
diabetes while pregnant, being around or in contact with dangerous
chemicals in the environment while pregnant, or using drugs or alcohol
during pregnancy (for more information about these factors and their
effects on prenatal health, visit the Prenatal Care--Healthy Behaviors section of this Web site)
These factors can change normal infant growth or development resulting in different types of birth defects, such as:
- Physical problems with body parts or structures--Some
physical problems include cleft (has a gap or split) lip or cleft
palate, heart defects, and abnormal limbs, such as a club foot.
- Functional
problems with how a body part or body system works--These problems are
often called developmental disabilities and can include things like:
- Nervous system or brain problems--such
as learning disabilities, behavioral disorders, speech or language
difficulties, muscle spasms or convulsions, and movement trouble
- Sensory problems--such as cataracts of the eyes, blindness, hearing loss, or deafness
- Metabolic disorders--involve
a body process or chemical pathway or reaction, such as conditions that
limit the body's ability to get rid of waste materials or harmful
chemicals
- Degenerative disorders--are conditions that might not be obvious at birth, but steadily make worse one or more aspects of health
In
some cases, birth defects can result for a combination of these
factors, or they can affect many parts or processes in the body, which
may lead to both physical and functional problems, to different degrees.
Some of these types of birth defects and developmental disabilities are described below.
Physical Birth Defects
Researchers and health care providers use the term neural tube defects
to describe one important category of birth defects. These problems are
related to the growth and development of the brain and spinal cord.
Neural tube defects can include conditions like anencephaly
(an-in-SEFF-a-lee), a fatal condition in which much of the brain does
not develop; and spina bifida, in which the membranes around the spinal
cord don't close properly, or the cord itself is not completely normal.
People with spina bifida may have difficulty walking or be unable to
walk without help, or they may have abnormal limbs. The condition is
also associated with other structural problems with the body. In half
of all babies born with spina bifida, the resulting problems are severe
enough to result in death.
Research in this area has shown that getting the right amount of folic acid
before and during pregnancy can prevent most neural tube defects. The
U.S. Public Health Service recommends that women of childbearing age
get at least 400 micrograms of folic acid each day, through food
sources and/or supplements. Health care providers recommend that women
supplement their diets with folic acid for three months before
conception, and then for at least the first three months of pregnancy.
Findings from research supported by the NICHD and other agencies
indicate that the right amount of folic acid can help prevent certain
birth defects and other problems during pregnancy. For more information
on this and other prenatal recommendations, please visit the Prenatal Care section of this Web site. For more information on this research, read the news releases about folic acid.
In
some cases, spina bifida can be detected in the womb. This early
detection may allow surgeons to correct the spinal cord problems before
birth, but researchers have yet to confirm this idea. If this research
proves effective, it could alleviate many of the lasting effects of
these problems. To learn more about this type of surgery, the NICHD is
supporting the MOMS (Management of Meningomyelocele Study) trial, a
clinical trial that will compare the safety and effectiveness of
surgery before birth, with surgery performed right after birth in
correcting spinal cord problems. The research is part of the Maternal-Fetal Medicine Unit (MFMU) Network,
an NICHD-supported program that uses 14 sites around the country to
conduct clinical trials related to the mechanisms of pregnancy and
birth. For more information, read the Institute's news release on the MOMS trial.
For additional information on spina bifida and neural tube defects, see the Additional Research and Other Resources on Birth Defects section below.
Functional Birth Defects/Developmental Disabilities
This
complex group of birth defects involves a problem with the operation of
a part of the body, a system in the body, or a process or pathway in
the body. Although this information groups these developmental
disabilities into general categories, many functional birth defects
affect multiple body parts or systems. For example, a metabolic
disorder may lead to nervous system or brain problems. This Web site
groups the information to make it easier to remember.
Nervous System/Brain Problems
As
mentioned above, some birth defects affect the functioning of the
brain, which can impact intelligence and learning. This section
describes some of the more commonly known functional birth defects.
Mental Retardation
The
term "mental retardation" describes a certain range of scores on an IQ
(intelligence quotient) test. Mental retardation can result from a
number of different birth defects, including:
- In the past, a specific type of bacterial infection, called Hib,
was a leading cause of mental retardation in the United States. But, as
a result of NICHD-supported research on this infection, researchers
funded by the NICHD were able to develop a vaccine to prevent the
infection from occurring. Since the discovery of the vaccine, Hib has been nearly eliminated in the United States, and in other areas where the vaccine is available. As a result, Hib is also no longer a cause of mental retardation in the United States and other areas.
- Down
syndrome describes a set of mental and physical characteristics related
to having an extra copy of a specific chromosome, Chromosome 21. This
set of symptoms includes mental retardation. Interventions and
treatments for the symptoms of Down syndrome can allow many individuals
with this condition to live healthy, productive lives. NICHD-supported
work in Down syndrome includes efforts to understand some of the other
problems associated with the condition, such as heart defects and early
mental decline.
- Fragile X syndrome is the most common
inherited form of mental retardation. Parents with few or no symptoms
can pass the condition on to their children through genes. A defect in a specific part of a specific gene, called the Fragile X Mental Retardation 1 gene, or FMR1,
causes the body to produce low amounts or none of a certain protein.
This protein is vital to normal brain development; without enough of
it, the brain doesn't grow properly, leading to the symptoms of Fragile
X. In 1991, NICHD-supported researchers were the first to identify that
a change in the FMR1 gene caused Fragile X. This and other
NICHD-supported research has continued in hopes of finding out what the
protein that is lacking or missing does in the brain. In response to
the Children's Health Act of 2000, the NICHD created three centers for
Fragile X research, to ensure that this work can continue. In addition,
the NICHD is working with other agencies and organizations dedicated to
understanding Fragile X to further knowledge about this condition. The
Institute's Families and Fragile X Syndrome publication
describes what is currently known about and what research is being done
to learn more about Fragile X. You can pre-order your free copy of this
booklet by e-mailing the NICHD Information Resource Center; please use "Fragile X" in the subject line, and be sure to include your mailing information.
For
additional information on mental retardation, or on any of the specific
conditions listed above related to mental retardation, see the Additional Research and Other Resources on Birth Defects section below.
Autism Spectrum Disorders
Other
developmental disabilities include problems like autism spectrum
disorders, a range of problems that can affect a person's ability to
communicate, social skills, and intelligence. Because autism is
diagnosed on a spectrum, people with this condition can be severely
affected, or have only mild symptoms; but they all have a type of
autism.
Understanding autism spectrum disorders is one of the top
priorities for the NICHD. To summarize and describe its research
efforts in this area, the Institute maintains the NICHD Autism Web Site.
Through this Web site, you can learn more about the current
NICHD-supported projects in this area, as well as the latest findings
from this research.
The Institute also provides publications on autism, in both English and Spanish. To learn more about the Institute's recent research findings in this area, read the news releases about autism.
In addition, the NICHD and other Institutes are currently sponsoring clinical trials on autism. The National Library of Medicine also provides information on autism.
Sensory-related Developmental Disabilities
Sensory-related
problems are often an important part of complex birth defect patterns.
For instance, children with congenital rubella, a collection of
problems that a child whose mother had rubella or German measles while
pregnant may have, are likely to be deaf, and to develop cataracts of
the eyes. Children with Williams syndrome have trouble seeing spatial
relationships between objects around them. Those with Fragile X
syndrome are often very sensitive to loud noises; they may overreact or
have outbursts in reaction to such sounds.
The NICHD's research
on birth defects has been helpful in understanding the timing of many
sensory-related birth defects. That is, the research allowed scientists
to pinpoint at what point in development certain problems occurred. The
National Institute on Deafness and Other Communication Disorders and the National Eye Institute
conduct and support research into various types of sensory-related
birth defects, their treatments and interventions, and different
services available for families affected by these conditions.
For additional information on sensory-related birth defects see the Additional Research and Other Resources on Birth Defects section below.
Metabolic Disorders
This
group of functional birth defects affects a person's metabolism, which
is the way the body builds up, breaks down, and otherwise processes the
materials it needs to function. For example, digestion, how your body
breaks down food into its smaller parts, is a metabolic process. Two
commonly known metabolic disorders include:
- Phenylketonuria
(fee-nill-key-toe-NERR-ee-uh), also called PKU, is a condition in which
a problem with a specific enzyme, a protein that speeds up certain
chemical reactions, causes mental retardation. NICHD-supported
researchers developed a dietary therapy that helps to balance the
amount of this enzyme in the body, which has almost eliminated mental
retardation in people with PKU. Conclusions from the NIH Consensus Development Conference on PKU: Screening and Management
recommend that this dietary therapy continue throughout life. Women
known to have PKU should follow the diet while they are pregnant to
prevent mental retardation in their children. The NICHD hopes to use
its successes with PKU research as a model for efforts on other
diseases.
- Hypothyroidism (high-poe-THIGH-roid-izm) is a
hormonal condition that, if left untreated in a pregnant woman, can
cause mental retardation in her baby. The thyroid is a gland in the body that makes a chemical signal called a hormone.
Hormones help to regulate certain functions in the body, including
puberty and pregnancy. Without enough thyroid hormone in the mother's
body, the fetus' brain won't develop correctly, resulting in mental
retardation. NICHD-supported researchers found that, by identifying
women who have this condition early in or before pregnancy, treatments
to get the level of thyroid hormone back to normal can prevent mental
retardation in some cases. In addition, NICHD research found that
children who are born with hypothyroidism could also be treated with
thyroid hormone to prevent many of the long-term effects of this
condition.
Degenerative Disorders
Some
infants born with degenerative disorders appear normal at birth, but
then lose abilities or functions due to the in condition. In these
cases, the defect is usually not detected until an older age, when the
child or person starts to show signs of a problem. Degenerative
disorder can cause physical, mental, and sensory problems, depending on
the specific defect.
In one type of degenerative disorder, early
onset X-linked adrenoleukodystrophy
(add-ree-know-loo-koe-diss-troe-fee), also called X-ALD, boys develop
normally until between ages four and eight. After this point, they
begin to lose brain and nervous system function. Eventually, boys with
X-ALD lose so much of their brain and neural abilities that they appear
to be in a "frozen" state, unable to move and communicate. X-ALD was
the focus of the movie Lorenzo's Oil, which described one family's
efforts to spur scientific progress.
Another type of degenerative birth defect is Rett syndrome. This disorder, which usually affects girls, is caused by a specific genetic abnormality.
The
NICHD's efforts to understand these types of birth defects focus on
screening techniques that allow early detection of these problems, and
strategies to treat or relieve some of the symptoms of these
conditions. Other work is underway to find the cellular mechanisms or
genetic markers for these conditions.
For additional information on degenerative birth defects see the Additional Research and Other Resources on Birth Defects section below.
Additional Research and Other Resources on Birth Defects
Research
on birth defects often begins by focusing on the specific effects of
the problem on an infant. Sometimes, the effects of birth defects can
be severe, such as not being able to walk, having organ systems that
aren't complete, or even death. Once scientists know the outcomes of a
certain problem, they can backtrack, following the problem back to
early stages of development to isolate when it might have happened.
Knowing when the problem first occurred can offer insight into how it
occurred.
Through this general scheme, NICHD-supported
researchers and their colleagues have made great progress in
understanding the characteristics of certain birth defects, the
patterns that these problems take, and possible points in growth and
development where the problems might occur. And, armed with this
understanding, researchers have developed interventions to prevent some
birth defects, methods of identifying birth defects early in
development, and possible treatments for birth defects.
The
NICHD's research on birth defects has not only improved the chances of
survival for those affected, but has also improved the quality of life
for many people impacted by birth defects and their families.
In addition to its research on specific types of birth defects, the NICHD recently announced the new NICHD Birth Defects Initiative.
By establishing a network of research sites, the Initiative will work
to develop an in-depth and thorough knowledge of birth defects, their
mechanisms, their outcomes, and their patterns. The NICHD feels that
this type of research is vital to creating a foundation of birth
defects resources that may lead to preventive and intervention
strategies.
The NICHD and other Institute are currently conducting a number of clinical trials related to birth defects.
Source: National Institute of Child Health and Human Development
Dr. Jeffrey Speller
Dr. Tanya Korkosz
Psychopharmacology Associates of New England
www.psychopharmassociates.com
