Search for Health Information You Need

Causes, Signs and Diagnosis of Birth Defects

Birth defects are sometimes referred to as congenital disorders or congenital anomalies. These defects are present when a baby is born or develop within the first month of birth. There are many kinds of birth defects, ranging from physical problems such hole in the heart and cleft palate, to degenerative diseases such as muscular dystrophy and nervous system/brain disorders like Down syndrome.

In the United States, birth defects are the most common cause of death during the first year of a baby’s life although many birth defects are non life-threatening and/or can be remedied with surgery or other treatments. Around three percent of babies in the US are born with a birth defect, the most common being cleft palate and Down syndrome.

Fast Facts about Birth Defects

  • There are thousands of different types of birth defect
  • In the US, birth defects are the most common cause of infant death
  • Around 3 percent of children in the USA are born with birth defects – the most common are Down syndrome and cleft palate
  • Birth defects may be genetic/chromosomal or environmental in origin
  • Environmental birth defects usually originate during the first three months of pregnancy and may be caused by smoking, alcohol, drugs (legal and illegal), poor nutrition, chemicals, ionizing radiation and infection

Types of Birth Defects

Broadly speaking, birth defects fall into one of several categories:

  • Structural defects – e.g. missing heart valves, cleft palate, limb abnormalities
  • Problems with the brain/nerves, including learning and developmental disorders like autism and Down syndrome
  • Problems with the senses – e.g. eyesight and hearing
  • Metabolic conditions where the body can’t process certain chemicals
  • Degenerative diseases such as cystic fibrosis and muscular dystrophy, which may not be apparent at birth but get worse over time

Common Causes of Birth Defects

Some birth defects are genetic in origin. Genetic birth defects may be inherited from one or both parents or they can be caused by chromosome problems that spontaneously occur when the mother’s egg is fertilized by a sperm cell. Examples of inherited birth defects include Tay-Sachs disease, cystic fibrosis and achondroplasia, which is a type of dwarfism. An example of a genetic birth defect resulting from chromosomal problems is Down syndrome, which is also known as trisomy 21 because it results in three copies of chromosome no. 21 in every cell rather than just a pair at this position. Other chromosomal birth defects are trisomy 18 (or Edwards syndrome) and Turner syndrome, which is also known as X monosomy because all or part of one X chromosome is missing.

Instead of being genetic or chromosomal in origin, some birth defects may be caused by factors in the environment. The risk of environmental birth defects is especially high if the mother is exposed to them during the first three months of pregnancy.

Examples of environmental factors that can cause birth defects include:

  • Certain infectious diseases such as German measles (rubella), toxoplasmosis and herpes
  • Certain prescription drugs, e.g. thalidomide and isotretinoin (Accutane) and vaccines made from live viruses, including the MMR vaccine
  • Smoking. This increases the chance of having stillborn or premature baby, and has also been linked to a number of specific birth defects including cleft palate, clubfoot and gastroschisis (where the intestines poke out through a hole in the abdomen)
  • Illegal drugs, including marijuana and ecstasy
  • Alcohol (which can cause fetal alcohol syndrome)
  • Ionizing radiation, including X-rays
  • Chemicals such as polychlorinated biphenyls (PCBs)
  • Poor nutrition during pregnancy

Environmental causes of birth defects are known as teratogens.

Risk Factors for Birth Defects

If you smoke, drink alcohol or take illegal drugs while pregnant then your unborn child is at greater risk of being born with an environmental birth defect.

Poor nutrition, including folic acid deficiency, has also been linked to birth defects such as spina bifida.

If you are on long-term medication and are thinking of having a baby, then you should discuss the risks with your doctor. You should also discuss any alternative/herbal medicines you are planning to take, as these too can cause birth defects.

Older women are more likely to have a baby with Down syndrome – women who become pregnant at the age of 45 have a one in thirty chance of giving birth to a Down syndrome child, as opposed to a chance of one in 1,300 at the age of 25.

Certain genetic birth defects such as cystic fibrosis are inherited from parents who are carriers of the disease.

Signs of Birth Defects

There are many different types of birth defect, all with different symptoms.

Diagnosing Birth Defects

Birth defects can often be diagnosed during pregnancy, via ultrasound, amniocentesis, chorionic villus sampling and blood tests. If a serious birth defect is found then the mother must make the difficult decision as to whether to have a termination.

Once a baby is born, some birth defects – particularly the physical/structural ones such as cleft palate and clubfoot – can be diagnosed simply by sight. Others, like heart valve disorders, may not make themselves apparent for weeks, months or even years. Tests such as X-rays and CT scans are useful for diagnosing birth defects of the heart. For other types of birth defect, the diagnostic tests used will depend on the situation.

Treatment Options for Birth Defects

The type of treatment – if any – will depend on the nature of the birth defect. Some defects – like hare lip, cleft palate or heart defects – can be corrected by surgery. Other conditions such as cystic fibrosis can be managed (but not cured). If your child is born with a birth defect, you should discuss the treatment options with your doctor.

Prevention of Birth Defects

If you are a woman trying for a baby, the risk of environmental birth defects can be minimized by making changes to your lifestyle such as cutting out cigarettes, drugs and alcohol, and ensuring that you eat a healthy diet that is rich in folic acid. If you are on any kind of medication, you should talk to your doctor about the possible risks for your unborn child.

Coping with Birth Defects

The prognosis/outlook very much depends on the kind of birth defect a child is born with. Some defects can be cured by a surgical procedure, while others require permanent adjustments to living arrangements and lifestyle, both for the child and the parents/carers.

Where to Get More Information:
Birth Defect Research for Children
National Birth Defects Prevention Network