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Birth Anomalies


Birth Anomalies (birth defects)

What are birth anomalies?

Birth anomalies (birth defects) are problems that happen as a baby develops in the mother's body. A birth anomaly may affect how the body looks, works or both. Some birth anomalies are so serious they can cause death; others are very minor problems that are easily repaired. Babies born with birth anomalies have a greater chance of illness and long-term disability than babies without birth anomalies.

What causes birth anomalies?

Most birth anomalies are caused by a complex mix of genetic, behavioral, and environmental factors. However, for many birth anomalies, exactly how these factors work together is unclear. Not all birth anomalies are preventable, but by taking preventive action there is an increased chance of having a healthy baby.

According to CDC, it is not clear how many birth anomalies are related to environmental exposures, such as chemicals, drugs, and ionizing radiation. Some chemicals, including polychlorinated biphenyls (PCBs), dioxins, and pesticides, are linked to nervous system anomalies and developmental problems such as reduced muscle tone and response. However, scientist need more data to make these connections clearer.

Living near a hazardous waste site is known as a risk factor for birth anomalies including: spina bifida, cleft lip or palate, gastroschisis, hypospadias, chromosomal congenital anomalies such as Down syndrome, and some heart and blood vessel defects. Exposure to disinfection by-products in drinking water such as trihalomethanes, or THM, may increase the risk of some types of birth anomalies which affect the brain and spinal cord, the urinary tract, and the heart.

Although some research on how environmental hazards might cause birth anomalies has been done, much more work is needed to understand the relationship between the environment and birth anomalies. Doctors and public health scientists know how some birth anomalies happen and, in some cases, can make recommendations to help prevent them. The causes of many other birth anomalies are unclear.

How to reduce risk:

Even though not all birth anomalies can be prevented women can increase their chances of having a healthy baby by managing health conditions and adopting healthy behaviors before becoming pregnant.

For more information on how to prevent birth anomalies and to learn about genetic counseling visit Oregon Health Authority's Preventing Birth Anomalies page.

Birth anomalies Oregon Environmental Public Health tracks:

Anencephaly: A serious birth anomaly in which a baby is born without parts of the brain and skull. It is a type of neural tube anomaly. These are anomalies that happen during the first month of pregnancy, usually before a woman knows she is pregnant.

Spina Bifida: A condition that affects the spine and is usually apparent at birth. Spina bifida can happen anywhere along the spine if the neural tube does not close all the way. The backbone that protects the spinal cord does not form and close as it should. This often results in damage to the spinal cord and nerves. Spina Bifida is reported without anencephaly.

Hypoplastic Left Heart Syndrome: A congenital heart anomaly that affects normal blood flow through the heart. As the baby develops during pregnancy, the left side of the heart does not form correctly.

Tetralogy of Fallot: A congenital heart anomaly that affects normal blood flow through the heart. It happens when a baby's heart does not form correctly as the baby grows and develops in the mother's womb during pregnancy.

Transposition of the Great Arteries (Vessels): A congenital heart anomaly in which the two main arteries going out of the heart—the pulmonary artery and the aorta—are switched in position, or transposed.

Cleft Lip: This happens if the tissue that makes up the lip does not join completely before birth. This results in an opening in the upper lip. The opening in the lip can be a small slit or it can be a large opening that goes through the lip into the nose. A cleft lip can be on one or both sides of the lip or in the middle of the lip, which occurs very rarely. Children with a cleft lip also can have a cleft palate.

Cleft Palate: This happens if the tissue that makes up the roof of the mouth does not join correctly. Among some babies, both the front and back parts of the palate are open. Among other babies, only part of the palate is open.

Hypospadias: A birth anomaly in boys in which the opening of the urethra (the tube that carries urine from the bladder to the outside of the body) is not located at the tip of the penis.

Gastroschisis: A birth anomaly of the abdominal wall. The baby's intestines stick outside of the baby's body, through a hole beside the belly button. The hole can be small or large and sometimes other organs, such as the stomach and liver, can also stick outside of the baby's body.

Upper Limb Reduction Anomalies: Occurs when a part of or the entire arm of a fetus fails to form completely during pregnancy. The anomaly is referred to as a limb reduction because a limb is reduced from its normal size or is missing.

Lower Limb Reduction Anomalies: Occurs when a part of or the entire leg of a fetus fails to form completely during pregnancy.

Down Syndrome (Trisomy 21): A condition in which a baby is born with an extra chromosome. Chromosomes are small "packages" of genes in the body. They determine how a baby's body forms during pregnancy and how, as the baby grows in the womb and after birth, the baby's body functions. Normally, a baby is born with 46 chromosomes. Babies born with Down syndrome have an extra copy of one of these chromosomes. This extra copy changes the body's and brain's normal development and causes developmental and physical problems for the baby.

About the measures:

Oregon Tracking reports the following measure for each birth anomaly:

  • Average annual number of cases among live births over a 5-year period
  • Prevalence per 10,000 live births over a 5-year period

About the data:

The Oregon Tracking Program has data for 12 birth anomalies. These anomalies are monitored by Oregon Tracking because they are linked to environmental risk factors and are included in most birth anomaly monitoring programs.

Oregon Tracking receives the birth anomalies data from Oregon’s Birth Anomalies Surveillance System. This system finds cases of birth anomalies through data from vital statistics (birth and death certificates), hospital discharge data, Early Hearing Detection and Intervention (EDHI) data and Medicaid claims data.

As of October 1, 2015, birth anomalies diagnosis data are in ICD-10CM, whereas previous diagnosis data are in ICD-9CM. Birth anomaly cases identified during and after the transition period will not be comparable to previous reporting. Therefore, 5-year aggregates cannot be compared to one another over time.

Related Indicators

For more information, visit these websites:

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