Birth Defects and Congenital Anomalies | Symptoms and Causes

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What causes birth defects?

Most birth defects are caused by genetic or environmental factors or a combination of the two (multifactorial birth defects). In most cases, however, the cause is unknown.

Genetic or inherited causes include:

  • chromosomal defects – caused by too few or too many chromosomes, or problems in the structure of the chromosomes, such as Down syndrome and extra copy of chromosome 21 and sex chromosome abnormalities
  • single gene defects – a mutation in one gene causes the defect
  • dominant inheritance – when one parent (who may or may not have the disease) passes along a single faulty gene, such as achondroplasia and Marfan syndrome
  • recessive inheritance – when both parents, who do not have the disease, pass along the gene for the disease to the child, such as cystic fibrosis and Tay Sachs

An environmental cause can include a drug, alcohol or a disease the mother has that can increase the chance for the baby to be born with a birth defect. An agent that can cause a birth defect is known as a teratogen.

Multifactorial birth defects are caused by a combination of genes and environmental exposures. In other words, a person can inherit a gene that increases sensitivity to an environmental trigger. Examples include cleft lip or palate, certain heart defects, and neural tube defects.

How can I lower my chances of having a child with a birth defect?

There are many steps a woman can take to lower her chances of having a child with a birth defect, including staying healthy before deciding to become pregnant. That's because a woman often does not know she is pregnant in the first few weeks, which can be crucial for the health and development of the baby.

Other steps you can take throughout your pregnancy include:

  • Stop smoking – Babies born to mothers who smoke tend to be lower birthweight; in addition exposure to secondhand smoke can harm the fetus
  • Eat a healthy diet – Eating a balanced diet before and during pregnancy is not only good for the mother's overall health, but essential for providing the developing fetus with essential nutrients for proper growth and development.
  • Maintain a healthy weight – Women who are overweight may experience medical problems such as high blood pressure and diabetes, and women who are underweight may have babies with low birthweight.
  • Medical management of preexisting conditions – Take control of any current or preexisting medical problems, such as diabetes or high blood pressure.
  • Folic acid – Taking 400 micrograms of folic acid each day can help lower the risk of neural tube defects, or birth defects of the brain and spinal cord. The vitamin is also found in some green leafy vegetables, nuts, beans, citrus fruits and fortified breakfast cereals.
  • Avoid exposure to alcohol and drugs during pregnancy – Be sure to inform your physician of any medications and herbal supplements you are taking, since they can all have adverse effects on the developing fetus.
  • Avoid exposure to harmful substances – These include lead, pesticides and radiation (i.e., X-rays), which may harm the developing fetus.
  • Lower your risk for infection. Pregnant women should avoid eating undercooked meat and raw eggs and avoid all contact and exposure to cat feces and cat litter, which may contain a parasite, toxoplasma gondii, that causes toxoplasmosis. Other sources of infection include insects that have been in contact with cat feces.
  • Take a daily vitamin – Begin taking a prenatal vitamin daily, prescribed by your doctor, to make sure your body gets all the necessary nutrients and vitamins needed to nourish a healthy baby.
  • Dealing with domestic violence – Women who are abused before pregnancy may be at risk for increased abuse during pregnancy. Your doctor can help you find community, social and legal resources to help you deal with domestic violence.
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- Sandra L. Fenwick, President and CEO

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