Birth defects

About Birth defects

Birth defects (also called congenital malformations) are conditions that happen when a baby does not develop normally during pregnancy. Structural defects may include missing limbs, malformed hearts, spina bifida and genetic conditions like Down Syndrome. Most birth defects happen during the first three months of pregnancy and are detected within the first year of life. Some birth defects (such as cleft lip or clubfoot) are easy to see, but others (such as heart defects or hearing loss) are found using special tests (such as x-rays, CT scans, or hearing tests). Birth defects can vary from mild to severe.

This site provides data on NYC children born with one or more of 12 major birth defects. Each of the 12 birth defects is defined in the glossary on this site. The data comes from the NYS Department of Health Congenital Malformations Registry.

Birth Defects and the Environment

Scientists believe most birth defects are caused by a complex mix of factors including our genes, behaviors and environment. However, the causes of most birth defects are unknown. The fetus is more sensitive to exposures than an adult and if exposures happen during important periods of development, birth defects may result. Although there has been some research into how environmental exposures might cause birth defects, there is still much more work that needs to be done to understand the relationship of these exposures to birth defects.

Known and probable risk factors for birth defects include the following: smoking, use of alcohol and other drugs, poor nutrition and/or health (such as low levels of folic acid, obesity and poorly controlled diabetes), some medicines (prescription & over-the-counter), toxic chemicals (such as lead, paint and paint thinner, gasoline, pesticides, and secondhand smoke), infectious agents (such as rubella and toxoplasmosis) and ionizing radiation (x-rays).

About the Data and Indicators

Collecting and sharing good data about the occurrence of birth defects is a first step in understanding how they might be related to the environment. Looking at patterns of birth defect rates can help health officials plan services and create ideas for research into environmental causes of birth defects.

All birth defects in any child less than two years old are reportable under New York State law to the State Congenital Malformations Registry.

Most birth defect reports are abstracted from inpatient hospital records, since birth defects diagnosed on an outpatient basis are not well reported.

Accurate hospital clinical recognition of birth defects depends on clinical expertise and interest. This is particularly true of conditions more difficult to diagnose. As a result, identification of birth defects may vary by area and by time. Areas with hospitals that provide higher levels of care may have more thorough diagnoses and, thus, apparently higher rates. Similarly, areas with hospitals that report cases more completely will also appear to have higher rates.


Not all birth defects can be prevented, but actions that increase the chance of having a healthy baby include:

  • Have regular medical checkups and check with a provider before taking any medications.
  • Eat healthy foods and maintain a healthy weight; avoid alcohol and don’t use street drugs.
  • Make sure that medical conditions like diabetes are under control.
  • Take a vitamin with folic acid before and during pregnancy.
  • Quit smoking and avoid exposure to secondhand smoke.
  • Damaged lead-containing paint in homes should be safely addressed by properly trained workers, ideally prior to pregnancy.  Pregnant women and small children should stay out of the home until lead paint projects are completed.
  • Employers should provide workplaces free from unsafe chemical exposures and provide protective gear to workers when necessary. To learn more about the chemicals at work, employees can ask their employer for the Material Safety Data Sheets for the products used.

Key Messages

About one out of every 33 babies is born with a birth defect. A birth defect can affect almost any part of the body. The well being of the child who is born with a birth defect depends mostly on which organ or body part is involved, how much it is affected and the quality of rehabilitative support received in early childhood.

Heart defects make up about one-third to one-fourth of all birth defects, affecting about one in every 100 to 200 births. Some of these heart defects can be serious, and a few are very severe.

Other common birth defects are “neural tube defects,” which are defects of the spine (spina bifida) and brain (anencephaly). They affect about one of every 1,000 pregnancies. These defects can be serious and are often life threatening.

Birth defects of the lip and roof of the mouth, known as “orofacial clefts,” include cleft lip, cleft palate, and combined cleft lip and cleft palate. These defects are also common and occur in about one in 700 to 1,000 babies.

Note: We are no longer updating birth defects data on this site. Much is unknown about the relationship between environmental exposures and birth defects. Research is ongoing. New York State tracks and collects birth defects information here.

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Anencephaly is a serious birth defect in which a baby is born without parts of the brain and skull.

Cleft lip (with or without cleft palate)

Cleft lip is a birth defect that occurs when a baby's lip does not form properly during pregnancy.

Cleft palate (without cleft lip)

Cleft palate is a birth defect that occurs when a baby's mouth does not form properly during pregnancy.

Down Syndrome (Mother under age 35)

Down syndrome is a condition in which a person has an extra chromosome. It causes delays in physical growth, and intellectual disabilities.

Down Syndrome (Mother age 35 and up)

Down syndrome is a condition in which a person has an extra chromosome. It causes delays in physical growth, and intellectual disabilities.


A birth defect where there is a hole beside the belly button and the baby's intestines or other organs are outside the baby's body.

Hypoplastic left heart syndrome

A rare birth defect where part of the heart is underdeveloped.


A birth defect in male babies where the urethra opening is not at the tip of the penis.

Lower limb Deficiencies

Lower limb deficiencies include undergrowth, overgrowth, failure of formation, and other variations or deficiencies in the lower limbs.

Spina bifida (without anencephaly)

Spina bifida is a neural tube defect that can cause cause physical and intellectual disabilities.

Tetralogy of Fallot

Tetralogy of Fallot is a congenital heart defect that affects how blood flows through the heart.

Transposition of the great arteries (vessels)

Transposition of the great arteries or vessels is a congenital heart defect that involves abnormal arrangement of parts of the heart.

Upper limb deficiencies

Upper limb deficiencies include undergrowth, overgrowth, failure of formation, and other variations or deficiencies in the upper limbs.