What are birth defects?
A birth defect is something abnormal about your newborn baby’s body. Every four and a half minutes, a baby in the United States is born with a birth defect. A defect, which can affect almost any part of your baby’s body, can be:
- Visibly obvious, like a missing arm or a birthmark.
- Internal (inside the body), like a kidney that hasn’t formed right or a ventricular septal defect (a hole between the lower chambers of your baby’s heart).
- A chemical imbalance, like phenylketonuria (a defect in a chemical reaction that results in developmental delay).
Your baby can be born with one birth defect such as a cleft lip (a gap in their upper lip) or multiple birth defects such as a cleft lip and cleft palate (a hole in the roof of their mouth) together, or even a cleft lip and cleft palate with defects of the brain, heart and kidneys.
Your healthcare provider won’t be able to detect all birth defects right when your baby is born. Some defects, such as scoliosis, might not be apparent until your child is several months old. An abnormal kidney might take years to be discovered.
How common are birth defects?
Birth defects are common. Between 2% and 3% of infants have one or more defects at birth. That number increases to 5% by age one (not all defects are discovered directly after your child’s birth). One out of every 33 babies born in the United States are affected by birth defects.
What are some other examples of birth defects?
- Duodenal atresia, an obstruction in the small intestine. It can cause polyhydramios (extra fluid around the fetus in pregnancy), which can increase the risk of preterm birth. It is sometimes associated with other genetic syndromes.
- Dandy walker malformation, an abnormal development of the posterior fossa (a space in your baby’s skull) and cerebellum (a section of the brain). This birth defect can cause a variety of problems.
- Limb defects, which happen when the fetal amnion (the inner lining of the amniotic sack) wraps around parts of the fetus (like a finger or foot).
Symptoms and Causes
What causes birth defects?
Experts don’t know the exact cause of most birth defects, but some reasons are:
- Genetic or hereditary factors.
- Infection during pregnancy.
- Drug exposure during pregnancy.
How do genes and chromosomes affect birth defects?
About 20% of birth defects are caused by genetic or hereditary factors. Genetic causes of birth defects fall into three general categories:
- Chromosomal abnormalities.
- Single-gene defects.
Every human body cell contains 46 chromosomes, and each chromosome contains thousands of genes. Each gene contains a blueprint that controls development or function of a particular body part. People who have either too many or too few chromosomes will therefore receive a scrambled message regarding anatomic development and function.
Down syndrome is an example of a condition caused by too many chromosomes. Because of an accident during cell division, individuals with Down syndrome have an extra copy of a particular chromosome (chromosome 21). This extra chromosome can cause a typical constellation of birth defects. Characteristic features of Down syndrome can include developmental delay, muscle weakness, downward slant of the eyes, low-set and malformed ears, an abnormal crease in the palm of the hand and birth defects of the heart and intestines.
With Turner syndrome, a female lacks part or all of one X chromosome. In the affected women, this can cause short stature, learning disabilities and absence of ovaries.
Trisomy 13 (Patau Syndrome) and Trisomy 18 (Edwards Syndrome) are caused by inheriting extra copies of the 13th or 18th chromosome, respectively. These are rarer, more serious conditions which cause severe birth defects that are incompatible with survival after birth.
In addition to inheriting an extra or absent chromosome, deletions or duplications of single genes can also cause developmental disorders and birth defects. One example is cystic fibrosis (a disorder that causes progressive damage of the lungs and pancreas).
Defective genes can also be caused by accidental damage, a condition called “spontaneous mutation.” Most cases of achondroplasia (a condition that causes extreme short stature and malformed bones) are caused by new damage to the controlling gene. In addition, recombination errors can cause translocations of chromosomes which may lead to complex birth defects.
How do environmental factors like infection and drugs affect birth defects?
Environmental factors can increase the risk of miscarriage, birth defects, or they might have no effect on the fetus at all, depending on at what point during the pregnancy the exposure occurs.
The developing fetus goes through two major stages of development after conception. The first, or embryo stage, occurs during the first 10 weeks after conception. Most of the major body systems and organs form during this time. The second, or fetal stage, is the remainder of the pregnancy. This fetal period is a time of growth of the organs and of the fetus in general. Your developing fetus is most vulnerable to injury during the embryo stage when organs are developing. Indeed, infections and drugs can cause the greatest damage when exposure occurs two to 10 weeks after conception.
Some medicines and recreational drugs can cause birth defects, which are most severe when used during the first three months of pregnancy. Thalidomide, an anti-nausea medicine prescribed during the 1960s, caused birth defects called phocomelia (absence of most of the arm with the hands extending flipper-like from the shoulders).
There’s also isotretinoin, previously known as Accutane or Roaccutane. Isotretinoin is a retinoid, a man-made form of vitamin A that’s used to treat skin conditions. It causes fetal retinoid syndrome. Characteristics of fetal retinoid syndrome may include:
- Growth delay.
- Malformations of the skull and face.
- Abnormalities of the central nervous system.
- Abnormalities of the heart.
- Abnormalities of the parathyroid gland.
- Abnormalities of the renal, thymus gland.
Alcohol is the most commonly used drug that causes birth defects. Fetal alcohol syndrome is a term used to describe the typical birth defects caused by the pregnant person's alcohol use:
- Learning disabilities.
- Developmental delay.
- Poor coordination.
- Abnormalities of facial features.
Another environmental factor that can cause birth defects is uterine constraint. The fetus grows in the uterus and is surrounded by amniotic fluid (similar to being suspended in a bag of water) that cushions it from excessive pressure. If the sack of fibers that holds the fluid breaks, bands of fibers from the torn sack can press on the fetus and cause amniotic band syndrome (which can result in partial contraction of or amputation of an arm or leg). An inadequate amount of amniotic fluid can cause excessive pressure on the fetus, causing pulmonary hypoplasia (lack of development of the lungs).
Medical science has identified the cause of about 30% of birth defects. That means about 70% remain without a straightforward cause. As many as 50% to 70% of birth defects are sporadic, and their cause remains unknown. A combination of environmental and genetic factors can increase the risk of certain birth defects.
Diagnosis and Tests
When are birth defects diagnosed?
Healthcare providers can diagnose birth defects before birth, at birth and after birth. Most are found within your child’s first year.
How are birth defects diagnosed?
During pregnancy you may choose to be screened for birth defects and genetic disorders with ultrasounds or blood tests. If a screening test shows something abnormal, a diagnostic test is often recommended. First trimester screenings check for problems with the fetal heart, and for chromosomal disorders such as Down syndrome. The screening tests include:
- Maternal blood screen. Blood tests can measure protein levels or circulating free fetal DNA in maternal blood. Abnormal results can indicate an increased risk of a fetal chromosomal disorder.
- Ultrasound. An ultrasound looks for extra fluid behind the fetus's neck. That could be a sign of an increased risk of a heart defect or chromosomal disorder.
Second trimester screenings check for problems with the structure of the fetus's anatomy. The tests include:
- Maternal serum screen. Blood tests in the second trimester can screen for chromosomal disorders and/or spina bifida.
- Anomaly ultrasound. An anomaly ultrasound checks the size of the fetus and checks for birth defects.
More tests may be recommended if a screening test is abnormal. Such diagnostic tests are also offered to people with higher risk pregnancies. The tests include:
- Fetal echocardiogram. This is a focused ultrasound of the fetal heart, and may be ordered in certain high-risk pregnancies, or if a heart defect is suspected on anomaly ultrasound. Not all heart defects can be seen before birth.
- Fetal MRI. This may be ordered in cases of suspected birth defects, particularly of the fetal brain or nervous system
- Chorionic villus sampling. Your healthcare provider will collect a very small piece of the placenta for this test. It will be examined for chromosomal or genetic disorders.
- Amniocentesis. Your healthcare provider will collect a small amount of amniotic fluid. Cells are tested for chromosomal disorders and genetic problems like cystic fibrosis or Tay-Sachs disease. Amniocentesis can also test for certain infections such as cytomegalovirus (CMV).
Many birth defects may not be diagnosed until after your baby is born. They may be seen immediately, like a cleft lip, or diagnosed later. Keep an eye on your baby’s health and report any symptoms to your healthcare provider. Further tests may be needed.
Management and Treatment
How are birth defects treated? What surgeries or medicines may help?
Treatment depends on the diagnosis. Click on the following links to learn about treatments for these examples of birth defects:
Can birth defects be prevented? How?
Most birth defects can't be prevented. But there are steps you can take to promote a healthy pregnancy. These tips include:
- See your healthcare provider consistently.
- If you are trying to conceive, or if you are sexually active and not using contraception, take a prenatal vitamin with 400 mcg of folic acid.
- Contact your healthcare provider immediately if you think you’re pregnant.
- Don’t drink alcohol.
- Don’t smoke.
- Talk to your healthcare provider about any medications and supplements you’re taking.
- Avoid marijuana and illegal drugs.
Outlook / Prognosis
What’s the outlook/prognosis for birth defects?
The outlook of a birth defect depends on the type. Click on the following links to learn about the prognoses for these examples of birth defects:
What are the consequences of birth defects?
The topic of birth defects is a complicated and emotional one. Birth defects are common and can be caused by many different genetic and environmental factors. The fact that the majority of birth defects are without known cause can be frustrating to both parents and healthcare providers.
The topic is emotional in that you may be understandably upset when you learn that your child has a serious birth defect. You may feel that medical science should be able to prevent, or at least identify in advance, all possible birth defects. You may feel that someone is at fault. You might blame yourself. You might feel that you either did something that caused the defect or failed to do something that could have prevented it. This is almost never the case.
Sometimes parents feel that the obstetrician is at fault. (An obstetrician is a healthcare provider who specializes in treating women during pregnancy, delivery and recovery.) The parents might believe that the obstetrician could have ordered a test, prescribed a medication, or done something differently to prevent the defect. This is usually not the case, but an honest discussion with the healthcare provider can help address these concerns.
If you are a parent of a child with a birth defect, you should schedule appointments with your child’s healthcare provider at times when you can be present. You and the healthcare provider should thoroughly discuss possible causes, testing, treatment and referrals to specialists and support groups. You should continue these discussions and should continue asking questions until you are completely satisfied.
A note from Cleveland Clinic
The very last thing an expectant parent wants to hear is that there is something wrong with the fetus or with their infant. Most birth defects can’t be prevented, but you can take some steps to reduce the likelihood of environmental effects. Remember to always discuss your concerns with your healthcare provider and follow their instructions regarding screening tests, medications, etc.
Cleveland Clinic is a non-profit academic medical center. Advertising on our site helps support our mission. We do not endorse non-Cleveland Clinic products or services. Policy