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Birth differences (congenital anomalies)

8-minute read

Key facts

  • In Australia, about 3 in 100 babies are born with a health condition.
  • Birth differences, also known as congenital anomalies or birth defects, include any health condition that a baby is born with.
  • Your baby could be born with a health difference if you are exposed to harmful substances or if you catch certain infections while you’re pregnant.
  • Your chance of having a baby with a health difference goes up the older you get, especially after the age of 35.
  • You can reduce your baby’s chance of health differences by having a healthy lifestyle, avoiding certain medicines and taking a folate supplement from one month before you conceive.

What are birth differences (congenital anomalies)?

Birth differences include any health condition that a baby is born with. They are sometimes called congenital anomalies or birth defects.

In Australia, about 3 in 100 babies are born with a health condition. Some babies are born with more than one health condition.

Some conditions are mild, while others can be very serious. Some babies may be born with health conditions, but these aren’t always noticeable until they get older.

What are the main types of birth differences?

Many birth differences are structural. This means that one of your baby’s organs has not developed properly. Some examples are:

Some birth differences involve your baby’s chromosomes. Your baby might have too many chromosomes or not enough, or they might have an abnormal gene. Some examples are:

In other birth differences, a part of your baby’s body doesn’t work properly. Some examples are:

What are the main causes of birth differences?

Often, it’s not clear why a baby is born with a health condition. However, there are some things that can increase your baby’s risk.

Harmful substances

While you’re pregnant, you might be exposed to something that can harm your baby, such as:

The more you are exposed to these substances, the higher the risk of harm to your baby. It also depends on when you are exposed — the highest risk is in the first 3 months of pregnancy. However, many people who are exposed to harmful substances will have a baby without any health condition.

If you are male and exposed to harmful substances around the time your baby is conceived, it usually won’t cause your baby to have health conditions. However, after certain cancer treatments, your doctor might advise you to wait a few months before trying to conceive.


Some birth differences are caused by infections during pregnancy. The risk of harm to your baby depends on when in pregnancy you are infected.

Infections that can cause harm to your baby include:


If you or your partner have an abnormal gene or chromosome, you could pass it on to your baby. This could cause a health condition. For this reason, some people may choose to have genetic screening before trying to fall pregnant. This is available to anyone, although may come at an additional cost. A doctor, obstetrician, fertility specialist, midwife or genetic counsellor can request genetic screening for you.

Your age and health

The older you are when you give birth, the greater the chance that your baby will be born with a health condition — especially a chromosomal disorder such as Down syndrome. The risk goes up when you turn 35 and rises even further when you turn 40.

If you’re under 20 years, your baby also has a higher risk of being born with a health condition.

If you don’t have enough folate in your diet, your baby is at a higher risk of neural tube defects and cleft lip or palate.

Living with obesity or diabetes before you become pregnant also increases your baby’s chance of having a continuing health condition.

Can these health conditions be prevented?

Not all health conditions that continue from birth can be prevented. However, you can lower your baby’s risk by:

  • maintaining a healthy weight
  • avoiding smoking and drug use before you become pregnant
  • avoiding alcohol and other drugs when you’re pregnant
  • taking folate and iodine supplements — it’s important to start taking folate one month before you try to conceive
  • checking that any medicines you take are safe in pregnancy
  • getting vaccinated against rubella and chickenpox if you’re not immune

If there is a genetic disorder in your family, it’s a good idea to have genetic testing before trying to become pregnant.

Can these health conditions be detected during pregnancy?

Many structural conditions can be picked up on an ultrasound at 18 to 20 weeks.

There are several screening tests available to pick up chromosomal disorders such as Down syndrome. Some involve blood tests only, while some also require an ultrasound.

If a screening test shows that your baby is at higher risk, you might choose to do a diagnostic test, such as amniocentesis. This can tell you for sure whether your baby has a chromosomal problem or not.

If my baby has a health condition, how is my care managed during pregnancy and birth?

If tests show that your baby has a health condition, talk to your doctor or midwife about it. They might refer you to a genetic counsellor for information and support.

You may need to see a specialist to monitor your baby and discuss treatment options. Depending on what the condition is, there might be treatments available, such as surgery or a medicine.

How are health conditions managed after the baby is born?

A doctor will examine your baby from head to toe. They will arrange tests if they suspect anything.

All babies are offered a newborn screening test, known as the ‘heel prick test’, to check for a range of serious health conditions.

If any conditions are detected, it’s very important to talk to your baby’s doctor to find out what to do next.

Resources and support

If your doctor has told you that your baby has a health condition, you can read more by visiting the Australian birth Defects Society webpage.

To talk to a genetic counsellor, or learn more about when to access a genetic counselling service, visit the Genetic Counselling Australia website.

Speak to a maternal child health nurse

Call Pregnancy, Birth and Baby to speak to a maternal child health nurse on 1800 882 436 or video call. Available 7am to midnight (AET), 7 days a week.

Learn more here about the development and quality assurance of healthdirect content.

Last reviewed: March 2023

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