NASET Q & A Corner
Questions and Answers on
Birth Defects
Birth defects are structural changes present at birth that can affect almost any part or parts of the body (e.g., heart, brain, foot). They may affect how the body looks, works, or both. Birth defects can vary from mild to severe. The well-being of each child affected with a birth defect depends mostly on which organ or body part is involved and how much it is affected. Depending on the severity of the defect and what body part is affected, the expected lifespan of a person with a birth defect may or may not be affected. Birth defects are common, costly, and critical conditions that affect 1 in every 33 babies born in the United States each year. Every 4 ½ minutes, a baby is born with a birth defect in the United States. That means nearly 120,000 babies are affected by birth defects each year. This issue of NASET’s Q & A Corner comes from the Centers for Disease Control and Prevention (CDC) and will address common questions regarding birth defects.ts with disabilities.
What are Birth Defects?
Birth defects are structural changes present at birth that can affect almost any part or parts of the body (e.g., heart, brain, foot). They may affect how the body looks, works, or both. Birth defects can vary from mild to severe. The well-being of each child affected with a birth defect depends mostly on which organ or body part is involved and how much it is affected. Depending on the severity of the defect and what body part is affected, the expected lifespan of a person with a birth defect may or may not be affected.
How Common are Birth Defects?
Birth defects are common, costly, and critical conditions that affect 1 in every 33 babies born in the United States each year. Every 4 ½ minutes, a baby is born with a birth defect in the United States. That means nearly 120,000 babies are affected by birth defects each year.
How are Birth Defects Identified? Identifying Birth Defects
A birth defect can be found before birth, at birth, or any time after birth. Most birth defects are found within the first year of life. Some birth defects (such as cleft lip) are easy to see, but others (such as heart defects or hearing loss) are found using special tests, such as echocardiograms (an ultrasound picture of the heart), x-rays or hearing tests.
Birth defects can be diagnosed during pregnancy or after the baby is born, depending on the specific type of birth defect.
During Pregnancy: Prenatal Testing
Screening Tests
A screening test is a procedure or test that is done to see if a woman or her baby might have certain problems. A screening test does not provide a specific diagnosis—that requires a diagnostic test. A screening test can sometimes give an abnormal result even when there is nothing wrong with the mother or her baby. Less often, a screening test result can be normal and miss a problem that does exist. During pregnancy, women are usually offered these screening tests to check for birth defects or other problems for the woman or her baby. Talk to your doctor about any concerns you have about prenatal testing.
First Trimester Screening
First trimester screening is a combination of tests completed between weeks 11 and 13 of pregnancy. It is used to look for certain birth defects related to the baby’s heart or chromosomal disorders, such as Down syndrome. This screen includes a maternal blood test and an ultrasound.
Maternal Blood Screen
The maternal blood screen is a simple blood test. It measures the levels of two proteins, human chorionic gonadotropin (hCG) and pregnancy associated plasma protein A (PAPP-A). If the protein levels are abnormally high or low, there could be a chromosomal disorder in the baby.
Ultrasound
An ultrasound creates pictures of the baby. The ultrasound for the first trimester screen looks for extra fluid behind the baby’s neck. If there is increased fluid found on the ultrasound, there could be a chromosomal disorder or heart defect in the baby.
Second Trimester Screening
Second trimester screening tests are completed between weeks 15 and 20 of pregnancy. They are used to look for certain birth defects in the baby. Second trimester screening tests include a maternal serum screen and a comprehensive ultrasound evaluation of the baby looking for the presence of structural anomalies (also known as an anomaly ultrasound).
Maternal Serum Screen
The maternal serum screen is a simple blood test used to identify if a woman is at increased risk for having a baby with certain birth defects, such as neural tube defects or chromosomal disorders such as Down syndrome. It is also known as a “triple screen” or “quad screen” depending on the number of proteins measured in the mother’s blood. For example, a quad screen tests the levels of 4 proteins AFP (alpha-fetoprotein), hCG, estriol, and inhibin-A. Generally, the maternal serum screen is completed during the second trimester.
Anomaly Ultrasound
An ultrasound creates pictures of the baby. This test is usually completed around 18–20 weeks of pregnancy. The ultrasound is used to check the size of the baby and looks for birth defects or other problems with the baby.
Diagnostic Tests
If the result of a screening test is abnormal, doctors usually offer further diagnostic tests to determine if birth defects or other possible problems with the baby are present. These diagnostic tests are also offered to women with higher risk pregnancies, which may include women who are 35 years of age or older; women who have had a previous pregnancy affected by a birth defect; women who have chronic diseases such as lupus, high blood pressure, diabetes, or epilepsy; or women who use certain medications.
High resolution Ultrasound
An ultrasound creates pictures of the baby. This ultrasound, also known as a level II ultrasound, is used to look in more detail for possible birth defects or other problems with the baby that were suggested in the previous screening tests. It is usually completed between weeks 18 and 22 of pregnancy.
Chorionic Villus Sampling (CVS)
CVS is a test where the doctor collects a tiny piece of the placenta, called chorionic villus, which is then tested to check for chromosomal or genetic disorders in the baby. Generally, a CVS test is offered to women who received an abnormal result on a first trimester screening test or to women who could be at higher risk. It is completed between 10 and 12 weeks of pregnancy, earlier than an amniocentesis.
Amniocentesis
An amniocentesis is test where the doctor collects a small amount of amniotic fluid from the area surrounding the baby. The fluid is then tested to measure the baby’s protein levels, which might indicate certain birth defects. Cells in the amniotic fluid can be tested for chromosomal disorders, such as Down syndrome, and genetic problems, such as cystic fibrosis or Tay-Sachs disease. Generally, an amniocentesis is offered to women who received an abnormal result on a screening test or to women who might be at higher risk. It is completed between 15 and 18 weeks of pregnancy. Below are some of the proteins for which an amniocentesis tests.
AFP
AFP stands for alpha-fetoprotein, a protein the unborn baby produces. A high level of AFP in the amniotic fluid might mean that the baby has a defect indicating an opening in the tissue, such as a neural tube defect (anencephaly or spina bifida), or a body wall defect, such as omphalocele or gastroschisis.
AChE
AChE stands for acetylcholinesterase, an enzyme that the unborn baby produces. This enzyme can pass from the unborn baby to the fluid surrounding the baby if there is an opening in the neural tube.
After the Baby is Born
Certain birth defects might not be diagnosed until after the baby is born. Sometimes, the birth defect is immediately seen at birth. For other birth defects including some heart defects, the birth defect might not be diagnosed until later in life.
When there is a health problem with a child, the primary care provider might look for birth defects by taking a medical and family history, doing a physical exam, and sometimes recommending further tests. If a diagnosis cannot be made after the exam, the primary care provider might refer the child to a specialist in birth defects and genetics. A clinical geneticist is a doctor with special training to evaluate patients who may have genetic conditions or birth defects. Even if a child sees a specialist, an exact diagnosis might not be reached.
What are Possible Causes of Birth Defects?
Birth defects can occur during any stage of pregnancy. Most birth defects occur in the first 3 months of pregnancy, when the organs of the baby are forming. This is a very important stage of development. However, some birth defects occur later in pregnancy. During the last six months of pregnancy, the tissues and organs continue to grow and develop.
For some birth defects, like fetal alcohol syndrome, we know the cause. But for most birth defects, we don’t know what causes them. For most birth defects, we think they are caused by a complex mix of factors. These factors include our genes (information inherited from our parents), our behaviors, and things in the environment. But, we don’t fully understand how these factors might work together to cause birth defects.
While we still have more work to do, we have learned a lot about birth defects through past research. For example, some things might increase the chances of having a baby with a birth defect, such as:
- Smoking, drinking alcohol, or taking certain “street” drugs during pregnancy.
- Having certain medical conditions, such as being obese or having uncontrolled diabetes before and during pregnancy.
- Taking certain medications, such as isotretinoin (a drug used to treat severe acne).
- Having someone in your family with a birth defect. To learn more about your risk of having a baby with a birth defect, you can talk with a clinical geneticist or a genetic counselor.
- Being an older mother, typically over the age of 34 years.
Having one or more of these risks doesn’t mean you’ll have a pregnancy affected by a birth defect. Also, women can have a baby born with a birth defect even when they don’t have any of these risks. It is important to talk to your doctor about what you can do to lower your risk.
What Does Research Tell Us About Prevention of Birth Defects?
Not all birth defects can be prevented. But, there are things that a woman can do before and during pregnancy to increase her chance of having a healthy baby:
- Be sure to see your healthcare provider regularly and start prenatal care as soon as you think you might be pregnant.
- Get 400 micrograms (mcg) of folic acid every day, starting at least one month before getting pregnant.
- Don’t drink alcohol, smoke, or use “street” drugs.
- Talk to a healthcare provider about any medications you are taking or thinking about taking. This includes prescription and over-the-counter medications and dietary or herbal supplements. Don’t stop or start taking any type of medication without first talking with a doctor.
- Learn how to prevent infections during pregnancy.
If possible, be sure any medical conditions are under control, before becoming pregnant. Some conditions that increase the risk for birth defects include diabetes and obesity.
What are Notable Research Findings Regarding Birth Defects?
We know what causes some birth defects, such as Down syndrome and fetal alcohol syndrome. However, for many birth defects, the causes are unknown.1 Also, we don’t fully understand how certain factors might work together to cause birth defects. While there is still more work to do, we have learned a lot about birth defects through past research. For example:
Getting enough folic acid, a B vitamin, at least one month before getting pregnant and during early pregnancy lowers the risk of having a baby with serious birth defects of the brain and spine (neural tube defects). For this reason, all women who can become pregnant should be sure to get 400 micrograms of folic acid every day.
Drinking alcohol during pregnancy can cause the baby to be born with fetal alcohol spectrum disorders (FASDs). Pregnant women should not drink alcohol any time during pregnancy. Women also should not drink alcohol if they are trying to get pregnant or if they are sexually active and do not use effective birth control.
Smoking in the month before getting pregnant and throughout pregnancy increases the chance of premature birth, certain birth defects (such as cleft lip, cleft palate, or both), and infant death. Quitting smoking before getting pregnant is best. However, for women who are already pregnant, quitting as early as possible can still help protect against some health problems for the mother and baby.
Women who are obese when they get pregnant have a higher risk of having a baby with serious birth defects of the brain and spine (neural tube defects), some heart defects, and other birth defects.
Poor control of diabetes in pregnant women increases the chance for birth defects and might cause serious complications for the mother, too. If a woman with diabetes keeps her blood sugar well-controlled before and during pregnancy, she can reduce the chance of having a baby with birth defects.
Taking certain medications during pregnancy can cause serious birth defects, but the safety of many of the medications taken by pregnant women has been difficult to determine. If you are pregnant or planning a pregnancy, you should not stop taking medications you need or begin taking new medications without first talking with your doctor. This includes prescription and over-the-counter medications and dietary or herbal products.
How are We Tracking Data on Birth Defects?
The Metropolitan Atlanta Congenital Defects Program (MACDP)
MACDP is a tracking system for birth defects among children born to residents of certain counties of metropolitan Atlanta. In MACDP, information is gathered about all babies with birth defects who live in the Atlanta area. Established in 1967, MACDP was the nation’s first system for active data collection about birth defects. Active data collection means that committed staff members seek out information about birth defects and continually review medical records at multiple healthcare facilities in a given geographic area. Information obtained from MACDP is used to understand who is affected by birth defects, learn about other health outcomes due to birth defects, and provide data for education and health policy decisions leading to prevention of birth defects. The system also serves as a model to help other programs develop and implement new tracking methods.
State-Based Tracking Systems
CDC helps to support birth defects tracking systems in 14 states and territories in the United States. The tracking systems look for all babies with birth defects who live in their study area, which is important to understand the impact of birth defects in their population. These funded states and territories use the data to refer infants and children with birth defects to needed services and develop materials and interventions to help prevent birth defects. Identifying birth defects at a state level also strengthens public health officials’ ability to estimate how common these conditions are and evaluate risk factors that are important in their community. State-based birth defects tracking programs provide important insights into our continued efforts to prevent birth defects and support families affected by them.
National Birth Defects Prevention Network (NBDPN)
CDC supports and collaborates with the NBDPN. The NBDPN is a group of over 225 individuals working at the national, state, and local levels, who are involved in tracking, researching, and preventing birth defects. The NBDPN serves as a forum for exchanging ideas about tracking and researching birth defects and for providing technical support for state and local programs. Established in 1997, the NBDPN assesses the effect of birth defects on children, families, and the healthcare system. The network also identifies risk factors for birth defects. This information can be used to develop strategies to prevent birth defects and to assist families and their providers in preventing other disabilities in children with birth defects.
Centers for Birth Defects Research and Prevention
CDC funds the Centers for Birth Defects Research and Prevention , which collaborate on large studies such as the National Birth Defects Prevention Study (NBDPS; births 1997-2011) and the Birth Defects Study To Evaluate Pregnancy exposureS (also called BD-STEPS; began in 2014).These studies, which interview mothers of children with and without birth defects, work to identify risk factors for birth defects.
Established in 1997, NBDPS has made key contributions toward understanding the risk of specific medications when used just before and during pregnancy. Data from NBDPS has clearly demonstrated that obesity in the mother is a strong risk factor for a number of major birth defects. NBDPS studies have also confirmed that women who smoke during pregnancy have a higher risk of having a baby with a cleft lip, cleft palate, or both. BD-STEPS builds on the success from NBDPS. It presents an opportunity to further explore NBDPS findings and follow up on leads to better understand what causes birth defects.
The Centers for Birth Defects Research and Prevention, which collaborate on BD-STEPS, are in Arkansas, California, Georgia (CDC), Iowa, Massachusetts, New York, and North Carolina. For the NBDPS, study centers in New Jersey, Texas, and Utah also contributed data and expertise.
Learn more about the Centers for Birth Defects Research and Prevention
International Clearinghouse for Birth Defects Surveillance and Research (ICBDSR)
The ICBDSR brings together birth defects programs from around the world with the aim of conducting worldwide tracking and research to prevent birth defects and to improve the lives of people born with these conditions. CDC supports and collaborates with the ICBDSR as a way to gain knowledge and expertise on birth defects globally and to further our domestic goals and those of the international community.
Environmental Public Health Tracking (EPHT)
Environmental public health tracking is the ongoing collection, integration, analysis, interpretation, and dissemination of data on environmental hazards, exposures to those hazards, and health effects that may be related to the exposures.
CDC funds 26 state and local health departments to develop local tracking networks and to provide data to the CDC’s Tracking Network. Part of the data given to CDC includes 12 birth defects. The Tracking Network provides the prevalence of these defects and publishes updated data every year. The Tracking Network’s Data Sources Fact SheetCdc-pdf lists which grantee states provide birth defects data to the Tracking Network.
National Health and Nutrition Examination Survey (NHANES)
NHANES is a survey designed to look at the health and nutritional status of adults and children in the United States. The survey is unique in that it combines interviews and physical examinations, including the collection of blood samples.
