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Birth Defects
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Birth Defects Research

Photo of toddler playing at the computerMost 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:

  • 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.

  • 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.

  • 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.

  • 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.
“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

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:

  • Studies of how genes and the environment work together to cause birth defects.

  • Studies of how common medicines used during pregnancy affect the risk of birth defects.

  • 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.

  • Environmental sampling—testing samples of air, water, and soil in an area to find substances that could be related to birth defects.

  • 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.

  • 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.

  • 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.

  • 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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