Birth defects

Key points about birth defects

  • Birth defects affect about 4.5% of all babies born in New Zealand. 
  • Some may be found during prenatal tests, while others are not found until after the baby is born.
  • Risk factors include lacking folic acid, drinking alcohol, smoking cigarettes, drug use and some medicines during pregnancy, some types of infection, obesity and uncontrolled diabetes.
  • Not all birth defects can be prevented, but there are things you can do to increase your chances of having a healthy baby.
  • These include planning ahead and taking folic acid daily, avoiding harmful substances, choosing a healthy lifestyle and using appropriate medicines and vaccinations.
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A birth defect is a problem that is present at birth and happens when a baby is developing in their mother’s body. Most birth defects happen in the first 3 months of pregnancy because that is when the organs are developing.

A birth defect may affect the way the body looks, works or both. Some birth defects (such as cleft lip) are easy to see, but others (such as heart defects or hearing loss) are found using special tests. Birth defects can vary from mild to severe.

If your baby is born with a birth defect or other health condition, they may need special care at birth and later in life. You will be able to talk to your baby’s healthcare team about any questions or concerns you have.

A child born with a birth defect can still lead a normal and healthy life. Although these children may have challenges that other people don’t have, they can still do everything most other people do.

Researchers have identified thousands of different birth defects, but some are much more common than others. There are two main categories of birth defects: structural (how the body is formed) and functional (how the body works). In some cases, birth defects are caused by a combination of factors, leading to both structural and functional problems.

Structural birth defects

Structural birth defects relate to problems with how part of the body is formed. Some of the more common or serious problems include: 

  • cleft lip or cleft palate
  • heart defects, such as missing or misshaped valves
  • abnormal limbs, such as a clubfoot
  • neural tube defects, such as spina bifida, anencephaly or other problems related to the growth and development of the brain and spinal cord. 

Young baby with cleft palate looking over mother's shoulder

 Image credit: Canva

Functional birth defects

Functional, or developmental, birth defects are related to a problem with how a body part or body system works. They can lead to intellectual and developmental disability and can include:

For most birth defects, the cause is unknown, but it may be due to one of the following causes:

  • Genetics – one or more genes might have a change or mutation that results in them not working properly, as in cystic fibrosis.
  • Chromosomal problems – a chromosome or part of a chromosome might be missing or there may be an extra chromosome, as in Down syndrome.
  • Not getting enough of certain nutrients. For example, not getting enough folic acid before and during pregnancy is a key factor in causing neural tube defects.
  • Exposure to harmful substances such as alcohol, cigarettes or certain medicines.
  • Infections during pregnancy, such as rubella.

Not all birth defects can be prevented. However, you can increase your chances of having a healthy baby by adopting a healthy lifestyle and managing health conditions before you become pregnant.

The following factors increase your risk of having a baby with a birth defect: lack of folic acid, drinking alcohol immediately before and while you are pregnant, smoking cigarettes, using drugs and taking certain medications during pregnancy, as well as some types of infection, obesity and uncontrolled diabetes.

If you are planning to become pregnant, make a PACT with yourself to take the following actions:

  • Plan ahead and take 800mcg of folic acid every day. This can help prevent major birth defects of the developing brain and spine.
  • Avoid harmful substances, including alcohol, cigarettes and other drugs, and food-borne bugs. These can all cause complications in pregnancy and birth defects. See alcohol and pregnancy and smoking and pregnancy.
  • Choose a healthy lifestyle – try to achieve and maintain a healthy weight and keep diabetes under control. Obesity and poor diabetes control increases the chance of birth defects and other problems in pregnancy. See eating, drinking and watching your weight in pregnancy and pre-existing diabetes and pregnancy.
  • Talk with your healthcare provider about any medications you are taking and any vaccinations you may need. Certain medications can cause serious birth defects if they are taken during pregnancy. Most vaccinations are safe during pregnancy and some vaccinations, such as the flu vaccine, are specifically recommended during pregnancy. See pregnancy and immunisation.

Pregnancy is an exciting time, but it also can be stressful. Knowing that you are doing all that you can to get ready for pregnancy, staying healthy during pregnancy and giving your baby a healthy start in life will help you to have peace of mind. For more information, see our pregnancy section.

Pregnancy and newborn screening(external link)(external link) National Screening Unit
Birth defects and other health conditions(external link)(external link) March of Dimes, US
Specific birth defects(external link) Centers for Disease Control and Prevention, US, 2017


Alcohol and pregnancy – what you might not know(external link) HealthEd, NZ, 2021


  1. Birth Defects(external link)(external link) Medline Plus
  2. Facts about birth defects(external link) CDC
  3. Birth defects(external link)(external link) National Institute of Child Health and Development, US
  4. New Zealand birth defects registry(external link)(external link) NZBDR, 2014

Clinical guidelines 

Observation of mother and baby in the immediate postnatal period – consensus statements guiding practice(external link)(external link) Ministry of Health, NZ, 2012
Neural tube defects – management of infant(external link)(external link) Starship, NZ, 2017 
Nutrition and supplements during pregnancy(external link)(external link) BPAC, NZ 
BPAC article preconception care in general practice(external link)(external link)


NZ Foetal Medicine Network

The NZ Maternal Foetal Medicine Network supports the management of women with high-risk pregnancies including those with foetal anomalies. The network provides information for parents and health professionals regarding the antenatal management of high-risk pregnancies within NZ.

For more information: NZ Foetal Medicine Network(external link)(external link)

Genetic Health Services NZ

The Genetic Health Services New Zealand provides expert genetic advice, counselling and diagnostic services to patients and health professionals. Find out more about the service they provide(external link)(external link)

For further information on investigating specific genetic disorders see The NZ laboratory schedule tests and guidelines – genetic tests(external link)(external link)

The NZ Birth Defects Registry

The NZBDR, which is funded under a contract with Health New Zealand | Te Whatu Ora. For more information: NZ Birth defects registry(external link)(external link)

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Credits: Healthify editorial team. Healthify is brought to you by Health Navigator Charitable Trust.

Reviewed by: Dr. Jeremy Tuohy, Researcher & Clinician, University of Auckland

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