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Most
birth defects are thought to be caused by a complex mix of
factors. These factors include our genes, our behaviors, and
things in the environment. For some birth defects, we know the
cause. But for most, we don’t. And we don’t understand well how
factors work together to cause birth defects. Research helps us
answer many of these questions.
CDC has been doing research in this field for over 40 years. And
we have funded other scientists to do research in the US and
abroad. This page gives an overview of birth defects research.
Why We Do Birth Defects Research
Birth defects can cause lifelong problems with health, growth, and
learning. We want to find ways to prevent birth defects. To do that,
we need to know what causes them. Research gives us important clues
about the factors that might raise or lower the risk of having a
baby with a birth defect. Those clues help us develop sound public
health policies for prevention.
What We’ve Learned
So far, we have learned a lot about birth defects through research.
Here are some examples:
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Mothers who are obese when they get
pregnant have a higher risk of serious birth defects of the
brain and spine (neural tube defects). This tells us that
helping mothers to reach a healthy weight before they get
pregnant could prevent birth defects.
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Taking folic acid before getting pregnant
and in early pregnancy lowers the risk of having a baby with a
neural tube defect. This finding led to the advice that all
women who can get pregnant should take 400 micrograms of folic
acid daily. A study by CDC and researchers in China helped with
this finding.
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When a mother smokes a lot in the month
before getting pregnant through the third month of pregnancy,
her baby has a higher risk of having cleft lip, cleft palate, or
both. This finding tells us that women who smoke and are
planning to have a baby should quit smoking and get help with
quitting if they need it.
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Taking Accutane™ (isotretinoin), a drug
used to treat severe acne, during pregnancy causes severe birth
defects. This finding has led to efforts to lower a woman’s risk
of having a pregnancy affected by the drug.
Centers for Birth Defects Research and Prevention
To find genes, behaviors, and things in the
environment that are linked with a certain birth defect, you need
many cases of that defect. Each year in the United States, 120,000
babies are born with birth defects. But, the number of babies with
each kind of defect is often quite low. That means you need a very
large study group to have enough cases of each birth defect to find
meaningful data. A study that large takes a network of researchers
working together across the nation.
The Centers for Birth Defects Research and Prevention (CBDRP)
provide that network. These centers, funded by CDC, have been set up
in Arkansas, California,
Iowa, Massachusetts, New York, North Carolina, Texas, and Utah.
National Birth
Defects Prevention Study
The research centers take part
in the National Birth Defects Prevention Study (NBDPS). This
study is the largest ongoing, population-based study of its
kind. Case mothers are women who have had babies or
pregnancies affected by birth defects and control mothers
had babies with no birth defects. The goal of each center is
to talk to 300 case mothers [Table 1] and 100 control
mothers per year. The study has three parts: 1) specialized
doctors review all cases, 2) talk to the mothers, and 3)
collect cheek cell samples from the families. The doctors
make sure that the defect the child has belongs in our
study. When we talk to the mother we ask questions about the
pregnancy. Things we ask about are: earlier pregnancies,
illnesses, medications, work place, lifestyle factors, etc.
The cheek cells that are collected from the families are
used for genetic studies.
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“I can’t imagine not participating in this
tudy. My husband and I thought we had planned and prepared for
everything during my pregnancy but at 30 weeks gestation, we
were shocked to find out that our baby had a life threatening
birth defect. We didn’t have any family history of birth defects
and so we asked WHY this had happened to our baby.
The doctors could only guess about the cause of the birth
defect. No one had any clear answers. This research study is a
vital step in the right direction to answering those unanswered
questions of “Why?” and “How can this be prevented?”
-- A study participant |
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The NBDPS started interviewing mothers of
children born after October 1, 1997 and is ongoing. It provides a
rich data source for rare birth defects. Many families worry about
the health of their babies and this study will address some of their
questions. By helping with this study these families hope we can
find some of the answers. CDC oversees the research centers and is
the ninth site for the study.
CBDRP researchers have been studying combined data from all the
sites participating in the study. The first projects focused on common birth defects like
cleft lip, cleft palate, hypospadias (a defect of the penis), and
some types of heart defects. Researchers looked for links between
those defects and common exposures such as smoking, infection,
medication use, and intake of certain nutrients. Many findings have
been published in science and health journals. Many more are
forthcoming.
More About the Centers
for Birth Defects Research and Prevention and the National Birth
Defects Prevention Study
Future Directions for Birth Defects Research
for the Centers for Birth Defects Research and Prevention
Through the Centers for Birth Defects Research and Prevention and
the NBDPS, we have been building the infrastructure for birth
defects research for a decade. We have found some important clues
about the causes of birth defects. But there is still much to learn.
More resources are vital if we are to understand fully the complex
factors and mechanisms that lead to birth defects.
Some of the activities for future research include:
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Studies of how genes and the environment
work together to cause birth defects.
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Studies of how common medicines used during
pregnancy affect the risk of birth defects.
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Genetic mapping—looking at the DNA (genetic
make-up) of family members affected by a particular birth defect
to find out what role genes play.
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Environmental sampling—testing samples of
air, water, and soil in an area to find substances that could be
related to birth defects.
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Studies of biomarkers—finding signs that
the body has been exposed to toxic substances. Scientists often
look for these signs in a person’s blood or hair.
The ultimate goal of the CBDRP’s work is to
share findings that can inform recommendations, laws, messages, and
programs to prevent birth defects. The data can also be used to
measure how well prevention efforts are working.
U.S.-China Collaborative Project
For over 20 years CDC and the Peking University Health Science
Center (PUHSC) have collaborated on birth defects research. In the
mid 1990’s, CDC and PUHSC began evaluating a large-scale community
intervention program in China. In this program, they tested whether
giving women 400 micrograms of folic acid before and during early
pregnancy prevents neural tube defects (NTDs). Among the babies of
women who took the daily recommended amount of folic acid, the risk
of having a NTD dropped 85% in high-prevalence areas and 41% in
areas with prevalence similar to the United States. In addition,
research from this community intervention program showed that folic
acid use before and during early pregnancy did not increase a
woman’s risk for miscarriage or multiple births.
We are now using our China collaboration to explore topics such as
folic acid and infant death rates, congenital heart defects (CHD),
changes in blood level of folic acid with different folic acid
doses, and long-term evaluation of the women and children from the
community intervention program.
Select CDC Specific Research
In addition to collaborating with state and international partners
to look at birth defects risk factors, CDC staff also conducts other
research projects.
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Some study findings are showing that babies
with birth defects are living longer. To further look at this
issue, we linked CDC’s birth defects tracking data with the
Georgia death certificates and the National Death Index. We
found that long-term survival of infants with spina bifida,
encephalocele, and Down syndrome improved over time. We now are
looking at the survival of babies with other birth defects.
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Obesity before or during pregnancy can
contribute to poor birth outcomes such as preterm delivery, low
birth weight, and some birth defects. CDC recently used data
from the Baltimore-Washington Infant Study to look at whether a
woman’s weight could be a risk factor for giving birth to babies
with poor birth outcomes. Our results showed that obese women
are more likely to have babies that are very heavy (more than
about 8.8 lbs.) or heavier than expected given the length of the
pregnancy. Also, we also found an increased risk of preterm
delivery among women with very low weight. This study shows that
women should try to maintain a healthy weight before becoming
pregnant.
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The National Health and Nutrition
Examination Survey (NHANES) is a program of studies designed to
evaluate the health and nutritional status of adults and
children in the United States. The survey is unique in that it
com¬bines interviews and physical examinations. The CDC uses
information from this study to look at the population’s folic
acid intake as well as their blood levels of folic acid.
Key Birth
Defects
Research Findings
Birth
Defects Research Publications
For the Researcher – A Tool for Statistical Analysis
Date:
January 14, 2008
Content source: National Center on Birth Defects and Developmental
Disabilities
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