Anencephaly: what it is, how it is found and the support available

The neural tube is the structure in the early embryo that becomes the brain and spinal cord, and it normally closes during the first weeks of pregnancy. When the top end fails to close, the result is anencephaly. NHS England's GeNotes resource describes it as an extreme form of neural tube defect in which a baby develops without parts of the brain and skull. The forebrain and cerebrum are absent and there is no bony covering over the back of the head.

GeNotes explains that some basic reflexes can be present, but that without the cerebrum there can be no consciousness and the baby cannot survive. There is also an increased chance of other differences, including folded ears, cleft palate and heart conditions. Anencephaly is related to, but different from, spina bifida, in which the lower part of the neural tube is affected; the NHS says the 20-week scan checks for both.

Anencephaly is usually found during routine pregnancy scans. The NHS describes the 20-week scan, also called the anomaly scan, as an ultrasound that looks for 11 different conditions, including anencephaly, and that is usually done between 18 and 21 weeks. It adds that the scan cannot find every condition and that it is your choice whether to have it. GeNotes says anencephaly can typically be identified at the first trimester or dating scan, and that raised alpha-fetoprotein levels in the mother's blood or amniotic fluid are typically seen.

Being told that something is wrong on a scan can be overwhelming. You may be asked to wait for a second opinion or a specialist scan, and you can ask for time, for written information and for someone to come with you. It is reasonable to ask the sonographer or midwife to stop and explain what they can see.

GeNotes says that anencephaly is a complex condition likely caused by the interaction of several genetic and environmental factors. Genes involved in folate processing, such as MTHFR, have been identified, but no gene appears to play a major role and the exact cause remains unknown. Folate deficiency is the most significant environmental factor identified for anencephaly and other neural tube defects.

The NHS lists, for spina bifida, not getting enough folic acid or vitamin B12 in pregnancy, a close family member with spina bifida, and some medicines used in pregnancy such as sodium valproate or carbamazepine as factors that raise the chance of a neural tube condition. Most cases of anencephaly occur in people with no history of the condition in their family. It is not caused by anything a parent did or did not do during pregnancy, and many parents find it helpful to hear that said plainly.

GeNotes, which is written for clinicians, says the prognosis is very poor and that the options, including termination of pregnancy, should be discussed. If the family chooses to continue the pregnancy, it says routine ongoing fetal medicine appointments are unnecessary, although these pregnancies are often complicated by extra amniotic fluid (polyhydramnios) later on, which may need review. Delivery planning is based on maternal risks, and vaginal birth is not contraindicated. Early induction of labour may be considered to help a vaginal birth.

There is no known cure or standard treatment. GeNotes notes that case reports exist of babies with anencephaly becoming organ donors after delivery, and that this is an option that could be discussed sensitively with parents. Whatever you decide, this is your decision and your team should support it. You can ask about memory-making, naming, photographs, funeral arrangements and seeing a chaplain or other spiritual support, depending on what matters to you.

GeNotes says that after having a child with anencephaly the recurrence risk is 2% to 5%, rising to 10% if parents have had two affected children, which is similar to other neural tube defects. People who have had a pregnancy affected by anencephaly are recommended to take a higher dose of folic acid, 5 mg instead of 0.4 mg a day, before getting pregnant and until 12 weeks of pregnancy. Speak to your GP before conceiving, because the higher dose is a prescription medicine.

GeNotes lists Antenatal Results & Choices, GOV.UK guidance for parents and the charity Shine as resources for patients. Your maternity unit will have bereavement midwives and specialist staff who can support you before and after the birth, and your GP and health visitor can continue care afterwards. Many people also find talking with their partner, family and friends, or with a counsellor, helpful in the weeks and months after. It is common for grief to come in waves, and there is no right pace.

Antenatal screening, diagnosis, counselling and bereavement care for anencephaly are provided through the NHS maternity system, including fetal medicine units for confirmatory scans. Private scans can pick up problems too, but any finding should be referred straight into NHS fetal medicine and bereavement services so that you have continuity of care.