Key points about anencephaly

  • Anencephaly is when a baby's brain and head doesn't form properly when it's growing in the womb (uterus). 
  • Sadly, this means the baby dies before it is born or very soon afterwards.
  • Support and information are available for parents.
  • There is no cure or treatment for anencephaly but risk can be reduced by taking folic acid before and during early pregnancy.
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Anencephaly is when the neural tube that forms the brain and spinal cord doesn’t fully close at the top while the fetus is growing.It happens during the first 24 days of a pregnancy and is known as a neural tube defect (NTD). The most common types of NTDs are spina bifida and anencephaly.

With anencephaly, the brain doesn’t fully develop – there will be no forebrain (front part) and no cerebrum (the coordinating and thinking part). Often the rest of the brain isn’t covered over with skull and skin. Without a fully formed brain, the baby dies before or shortly after birth within hours or days.  

In Aotearoa 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. The number of pregnancies affected by NTDs is decreasing because there is more awareness of the importance of folic acid for babies’ development (see below).  

The image below shows how the front and top of the baby’s brain hasn’t developed and the top of the head has no bone or skin covering. 

Image of baby with brain and head not fully formed due to anencephaly

Image credit: Centers for Disease Control and Prevention, National Center on Birth Defects and Developments; Disabilities, Wikimedia Commons

The cause is not clear but it’s likely be due to a combination of genes and environmental factors, eg, diet and medicines. While it’s 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 1 month before getting pregnant and for the first 3 months of pregnancy can reduce the risk of having a baby with anencephaly and spina bifida.  Read more about folic acid in pregnancy.(external link) 

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 (see below).  

Use of anti-epileptic drugs also increases the risk of anencephaly, so if you're taking these medicines see your healthcare provider or specialist before you plan to become pregnant. 

Anencephaly can often 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. They can also tell you whether you or your baby are more likely to have a medical condition. Read more about antenatal screening tests. 

Screening tests used to diagnose anencephaly include:

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

Blood test:  If you have the second trimester maternal serum screening (a blood test taken between 14 and 20 weeks), one of the components measures how much alpha-fetoprotein (AFP) is in your blood. High levels of AFP may suggest the developing baby has a neural tube defect (eg, spina bifida or anencephaly) or some other developmental problem.

Diagnostic tests

If any of the screening tests suggest there's a higher risk of a genetic condition or anencephaly, further diagnostic testing will be arranged through your local Fetal Medicine team. Diagnostic tests include amniocentesis or chorionic villus sampling (CVS). If anencephaly is confirmed, what this means for you and your whānau will be explained as carefully as possible. You will be given time to decide what to do next. You may choose to continue with or terminate your pregnancy.

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

Anencephaly is clearly seen at birth. Most babies with anencephaly are stillborn.  

Sadly, there is no treatment. Because their brain hasn’t fully developed and lacks important parts, the baby dies before or shortly after birth. There’s no chance of survival.  

Talking with a trained counsellor can often be helpful in times like this. You and your whānau will usually be offered counselling through your local Fetal Medicine Unit. You can also find out more at Maternal Fetal Medicine Network(external link). The Network is a national organisation with hubs in Auckland, Wellington and Christchurch.  

Other support options include:  

  • Sands:(external link) A network of parent-run, non-profit groups supporting families who have experienced the loss of a baby. 
  • Grief counselling 
  • Check with your general practice – some have access to free counselling through health improvement practitioners (HIPs). Read more about HIPs.  

Research shows that women who have a high level of folic acid before they become pregnant, are less likely to have 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's still worth starting it as soon as you find out you're pregnant.

Wanting to get pregnant?

Ask your GP or nurse for a free folic acid prescription. You can also get this from your local pharmacy. The Ministry of Health recommends you take these folic-acid only tablets for at least 4 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 (eg, those who are taking certain medicines 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.

Watch 'The Short Life of Poe Elijah Williams a baby born with Anencephaly into Much Love' by Ozventures(external link)
Note: You may find this video upsetting.

Future pregnancies are not usually affected. However, there is a very small increased risk of having another baby with anencephaly. Your best chance of preventing it is to take the recommended amount of folic acid.  

Other websites

Antenatal screening(external link) National Screening Unit, NZ, 2014 
Neural tube defects (NTDS) – anencephaly – information for parents(external link) NHS, UK, 2020


Antenatal screening and testing for Down syndrome and other conditions in pregnancy(external link)  Health Promotion Agency and Ministry of Health, NZ, 2020 


  1. What is NTD?(external link) Health New Zealand | Te Whatu Ora
  2. Anencaphaly(external link)  Maternal Foetal Medicine Network, NZ, 2023
  3. Neural tube defects(external link) Patient Info, UK, 2023
  4. Facts about anencephaly(external link) Centres for Disease Prevention and Control, US, 2023 
  5. Neural tube defects (NTDS) – anencephaly – information for parents(external link)  UK Government (for NHS), 2020
  6. Non-invasive prenatal screening strategies(external link) MSD Manuals, NZ
  7. Amniocentesis(external link) Women’s Health Centre, NZ 
  8. Folate and folic acid(external link) Health New Zealand | Te Whatu Ora, 2023
  9. 5 ways to lower the risk of having a pregnancy affected by a neural tube defect(external link) CDC, US, 2023 

Screening and detection of anencephaly

The following information on screening and detection of neural tube defects is taken from Neural tube defects – management of infant(external link) Starship Clinical Guidelines, NZ, 2017.

Maternal Serum Alpha Feto Protein (MSAFP) is often done at 15-20wk to screen for trisomies. An elevated MSAFP 2 - 2.5 median value detects 80% open NTD and 90% anencephaly. Uncertain gestational age results in a 5% false positive rate. Amniotic Alpha Feto Protein (AFP) and Acetylcholinesterase are raised with open NTDs. The latter is specific for NTD while AFP is raised in other open defects eg. Gastroschisis.

USS: Diagnosis often made at 16-18 week USS. Often seen as lateral displacement of the spinal pedicles, but the sac may also be visualised. An axial cross section through the fetal skull may demonstrate a "lemon head" shape, with a depression of the metopic suture in the frontal region. Visualisation of the posterior fossa may demonstrate a "banana sign", observed at the level of the cerebellum and cistern magna. It is caused by herniation of the cerebellar vermis through the foramen magnum, giving the cerebellum the appearance of a banana. USS should evaluate for other structural abnormalities of limbs, brain, kidneys, and other organs.

Visit Neural tube defects – management of infant(external link)(external link) Starship Clinical Guidelines, NZ, 2017 for images of neural tube defects on ultrasound. 

Preventing anencephaly

Folic acid supplementation must begin before conception for it to be effective. There are subsidised 800 µg and 5mg folic acid tablets available over the counter from pharmacies in New Zealand. These folic-acid only tablets are recommended by the Health New Zealand | Te Whatu Ora for women for at least four weeks prior to conception and for 12 weeks after conception to reduce the risk of NTDs. Folate/folic acid(external link) Health New Zealand | Te Whatu Ora

Clinical guidelines and resources

Neural tube defects – management of infant(external link)(external link) Starship Clinical Guidelines, NZ, 2017
Edwards L, Hui L. First and second trimester fetal testing for structural anomalies(external link)(external link) Semin Fetal Neonatal Med. 2017 Dec 9. 
Guideline – optimal serum and red blood cell folate concentrations in women of reproductive age for prevention of neural tube defects(external link)(external link), World Health Organisation, US, 2015
Neural tube defects(external link)(external link) Patient Info, UK, 2014


anencephaly nz maternal fetal medicine network


Maternal Fetal Medicine Network, NZ, 2016

antenatal screening testing for down syndrome and other conditions in pregnancy

Antenatal screening and testing for Down syndrome and other conditions in pregnancy

Health Promotion Agency and Ministry of Health, NZ, 2020

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

Reviewed by: Dr Janine Bycroft, GP, Auckland

Last reviewed: