Anencephaly is a serious condition in which the brain, skull and scalp of a baby doesn’t develop during the pregnancy. Sadly, this means the baby dies before it is born or very soon afterwards. There is support and information available for parents.

Key points

  1. Anencephaly happens during the first 24 days of a pregnancy. This is when the neural tube that forms the brain and spinal cord grows. When this tube doesn’t close fully, it is known as a neural tube defect (NTD). The most common types of NTDs are spina bifida and anencephaly.
  2. With anencephaly, the brain doesn’t fully develop. The baby has only a partially formed brain, skull and scalp. Without a fully formed brain, the baby dies before or shortly after birth. 
  3. In New Zealand, 5 to 6 babies in every 10,000 pregnancies are born with anencephaly, although many more are diagnosed with this condition during pregnancy. 
  4. There is no treatment for anencephaly but the risk can be reduced by taking folic acid before you get pregnant.
Source: PharmaTutor, 2016

What are the causes of anencephaly?

Like most problems discovered at or before birth (known as congenital anomalies) there are many causes of anencephaly. While it is not possible to prevent all cases of anencephaly, it is possible to decrease the risk of having a baby with this condition.

Studies have shown that taking folic acid supplements for at least one month before getting pregnant and three months into a pregnancy can reduce the risk of having a baby with anencephaly and spina bifida.  Read more about folic acid in pregnancy.

If you have a family history of any NTD, your risk is higher and the dose of folic acid you take also needs to be higher to be effective.

Use of anti-epileptic drugs also increases the risk of anencephaly, so women taking these medications should see their doctor or specialist before they plan to become pregnant.

How is anencephaly diagnosed?

Anencephaly can be diagnosed during the optional screening tests you will be offered as part of your antenatal care. Screening tests can provide you with information about your baby’s growth and development and how your body is coping with the physical changes and demands of pregnancy. They can also tell you whether you or your baby are more likely to have a medical condition.

Screening tests that are used to diagnose anencephaly include:

Ultrasound scan: In most cases, signs of anencephaly are observed at the 11to 14-week scan, and if not, it will almost always be picked up at the 20-week scan.

Blood test: Anencephaly, and most forms of spina bifida, can also be diagnosed by a special blood test called a maternal serum alpha feto-protein (MS-AFP). This is taken between 14 and 20 weeks and is part of the second-trimester screening test for Down Syndrome and other conditions. The MS-AFP test measures how much alpha-fetoprotein is in your blood. High levels of AFP may suggest the developing baby has a neural tube defect such as spina bifida or anencephaly or some other developmental problem.

An amniocentesis is not needed to diagnose anencephaly but may sometimes be undertaken to see if the anencephaly is part of a more complex condition.

If anencephaly is suspected, your Lead Maternity Carer (LMC) will refer you to your local Foetal Medicine Unit. If the diagnosis is confirmed, what this means for you and your whānau will be explained as carefully as possible. You will be given time to decide about what to do next. You may choose to continue with or terminate your pregnancy. 

If a woman chooses not to have an ultrasound scan during pregnancy, anencephaly might not be diagnosed until after the baby is born.

Anencephaly is immediately seen at birth. Most of the babies with anencephaly are stillborn. 

What is the treatment for anencephaly?

Sadly, there is no treatment. Because the brain doesn’t fully develop, the baby dies before or shortly after birth. There is no chance of survival. 

What support is there with anencephaly?

You will be able to get pregnancy counselling through your local Fetal Medicine Unit for you and your whānau. Find out more at Maternal Fetal Medicine Network

Parent2ParentNZ A free information and support network for parents of children with special needs ranging from the very common to the rarest conditions.
Sands A network of parent-run, non-profit groups supporting families who have experienced the loss of a baby.

How can I prevent anencephaly?

Research shows that women who have a high level of folic acid before they become pregnant, are less likely to give birth to a baby with neural tube defects. For it to work, supplementation should begin before you try to get pregnant, but if you didn’t start folic acid before you were pregnant it is still worth starting it as soon as you find out you are pregnant.

There are subsidised folic acid tablets available over the counter from pharmacies. The Ministry of Health recommends you take these folic-acid only tablets for at least four weeks prior to conception and for 12 weeks after conception to reduce the risk of NTDs.

The recommended dose of folic acid for most women is 0.8 mg per day. Women who are at higher risk of having a baby with a neural defect, such as those who are taking certain medications or who have had a previous child with a neural tube defect, should take 5 mg of folic acid a day for at least a month before getting pregnant.

Read more about folic acid in pregnancy.

Learn more

Antenatal screening National Screening Unit, NZ, 2014
Anencephaly Maternal Foetal Medicine Network, NZ, 2016
Neural tube defects (NTDS) – anencephaly – information for parents NHS, UK, 2013
Neural tube defects Patient Info, UK, 2014


  1. What is NTD? Ministry of Health, NZ, 2016
  2. Anencephaly Maternal Foetal Medicine Network, NZ, 2016
  3. Neural tube defects Patient Info, UK, 2014
  4. Facts about anencephaly Centres for Disease Prevention and Control, US, 2015

Reviewed by

Dr Jeremy Tuohy is an Obstetrician and Gynaecologist with a special interest in Maternal and Fetal Medicine. Jeremy has been a lecturer at the University of Otago, Clinical leader of Ultrasound and Maternal and Fetal Medicine at Capital and Coast DHB, and has practiced as a private obstetrician. He is currently completing his PhD in Obstetric Medicine at the Liggins Institute, University of Auckland.
Credits: Health Navigator Editorial Team. Reviewed By: Dr Jeremy Tuohy Last reviewed: 26 Feb 2018