Anencephaly is a severe type of neural tube defect (NTD). In early pregnancy, the “neural tube” should close and form the baby’s brain and spinal cord. In anencephaly, the upper part of this tube does not close, so much of the brain and skull do not form. Most affected pregnancies end in miscarriage or stillbirth. Newborns who are born alive typically survive only hours to days. There is no treatment that reverses or repairs the condition. CDC+1
Anencephaly is a very severe birth defect of the brain and skull. In early pregnancy, a flat tube of tissue (the “neural tube”) must fold and close to form the baby’s brain and spine. In anencephaly, the top (head) end of this tube does not close. Because of that, large parts of the brain and the skull bones do not form. Babies with anencephaly are born without most of the brain’s thinking areas (cerebral hemispheres) and without the protective skull above them. Sadly, this condition is fatal and there is no cure. CDC+1
The neural tube normally closes by the 3rd–4th week after conception—often before a person knows they are pregnant. If closure fails at the head end, the skull and brain above the brainstem do not develop. The hindbrain may remain, but the cerebrum and cerebellum are severely reduced or absent, which is why long-term survival is not possible. Medscape
Other names
Doctors may also use terms like cranial NTD, holoanencephaly, meroanencephaly (partial), exencephaly (an earlier stage where brain tissue is exposed), or craniorachischisis (when the open defect extends down the spine). These words describe how much of the head and sometimes the spine did not form normally. Ultrasound descriptions such as the “frog-eye sign” (prominent orbits with absent cranial vault) also point to anencephaly. Radiopaedia+2PMC+2
During weeks 3–4 of pregnancy, the neural tube should close. If the head end fails to close, the skull and most of the forebrain do not develop. The brain tissue that is exposed to the amniotic fluid breaks down over time. This is why early scans may show acrania or exencephaly, and later scans show anencephaly. BrainFacts+1
Types
Doctors sometimes describe anencephaly by how much tissue is missing or which regions are involved:
Meroanencephaly (partial) — partial absence of brain tissue and skull; considered a “classic” form. Some brainstem structures may remain. PMC
Holoanencephaly (total) — near-total absence of the brain above the brainstem. CDC Archive
Craniorachischisis — the most extensive form: anencephaly with an open spine (the defect continues down the back). CDC Archive
Exencephaly → anencephaly sequence: exposed brain tissue degenerates over time.
Craniorachischisis: anencephaly plus an open spine. Radiopaedia+1
- Acrania–Exencephaly–Anencephaly sequence (AEAS) — a recognized developmental sequence: first the skull is absent (acrania), then the exposed brain tissue bulges and degenerates (exencephaly), and finally most brain tissue is lost (anencephaly). Clinicians use these linked terms because ultrasound can show different stages at different weeks. PMC
Causes
Important note: In many pregnancies there is no single cause. Several risks can add together. Taking folic acid before pregnancy lowers the risk for neural tube defects (NTDs) like anencephaly. CDC+2World Health Organization+2
Low folate (no folic acid supplement before pregnancy). Folate is needed for cell growth and tube closure. Not taking 400 µg folic acid daily before conception and in early pregnancy increases NTD risk. CDC+2World Health Organization+2
Previous pregnancy with an NTD. Once a family has had an NTD, the chance is higher in the next pregnancy without high-dose folate; guidelines advise 4 mg/day in high-risk women. Guideline Central
Maternal diabetes (pre-existing). High blood glucose around conception is linked to more NTDs. Good control before pregnancy reduces risk. PMC
Maternal obesity. Obesity is associated with a higher chance of NTDs, possibly via metabolic and folate-related pathways. AJOG+1
Maternal hyperthermia (high body temperature) in early pregnancy. Fever, hot tubs, or saunas that raise core temperature early in the first trimester are linked to NTDs. PubMed+1
Valproate (valproic acid) exposure. This anti-seizure/mood drug has a well-documented teratogenic risk, including NTDs; it should be avoided in pregnancy when possible. FDA Access Data+2Default+2
Other anti-seizure medicines at higher risk (e.g., some exposures to carbamazepine, topiramate). Risk is lower than with valproate but still elevated compared with no exposure. Decisions require specialist care. PMC
Folate-antagonist medicines (e.g., methotrexate, trimethoprim combinations) near conception. These can interfere with folate-dependent closure. (Clinical caution is advised.) Cochrane Library
Low vitamin B12 status. Low B12 has been associated with higher NTD risk in some studies, possibly interacting with folate pathways. PMC
Certain genetic variants in the baby (e.g., planar-cell-polarity genes). Rare gene changes in pathways that control neural tube bending and closure can contribute. PMC
Low overall maternal nutrition/food insecurity. Poor micronutrient intake around conception increases NTD risk; population folic acid fortification reduces it. PMC
Short time between pregnancies. When nutrition has not recovered, risk factors (like low folate) can persist; clinicians consider spacing and supplementation. (Inference from nutrition & prevention guidance.) CDC
Maternal infections with high fever in very early pregnancy. The heat itself (rather than the germ) appears to be the harmful factor for tube closure. PubMed
Environmental or occupational teratogens. Some chemicals and toxins have been linked to NTDs in research; specific exposures vary by setting and study. PMC
Folate-poor diet (no fortified foods). In countries without food fortification, baseline NTD rates are higher; supplements are strongly recommended. PMC
Maternal age (extremes). Some studies note modest associations at very young or older ages; effects are small compared with folate, diabetes, or drugs. PMC
Passive smoke exposure. Some analyses link household smoke to higher NTD risk; more studies are ongoing. PMC
Influenza illness with fever early in pregnancy. The risk seems tied to the fever/hyperthermia component. PMC
Low socioeconomic status. Often reflects nutrition gaps and less access to preconception care and supplements, raising risk at the population level. PMC
Multifactor combination (gene–environment). For many families, risk reflects several small factors rather than one cause; folate remains the proven protective step. Cochrane Library
Symptoms and signs
Remember: anencephaly is usually recognized before birth on ultrasound. These features describe what scans show and what is seen at birth. AJOG
Very abnormal head shape on scan. Early scans may show missing skull bones; later scans show the upper skull absent and brain tissue missing. PMC
“Mickey-Mouse”-like crown on first-trimester scan. Because the skull is absent, brain tissue may bulge and look like two lobes above the orbits. Fetal Health Foundation
Absent calvarium (skull cap). The bony skull covering is missing above the orbits; this is a key clue on ultrasound. obgyn.onlinelibrary.wiley.com
Progression from acrania → exencephaly → anencephaly over weeks. The exposed tissue degenerates; the final picture is anencephaly. PMC
Very small or unmeasurable biparietal diameter and head circumference. Standard head measurements cannot be obtained or are extremely abnormal. NCBI
Polyhydramnios (too much amniotic fluid). Swallowing is impaired, so fluid builds up; ultrasounds often note this late in pregnancy. ScienceDirect
At birth: missing scalp and skull over the top of the head. The defect is immediately obvious on physical exam. CDC Archive
No conscious awareness. The cortex is absent; babies are permanently unconscious, although some brainstem reflexes may remain. New England Journal of Medicine
Possible primitive reflexes (e.g., breathing, startle). These are brainstem-level responses and do not mean awareness. New England Journal of Medicine
Feeding cannot be coordinated. Without higher-brain control, sucking and swallowing are not sustained for life. CDC
Eye and facial differences. Low-set ears, short neck, or other minor anomalies may be seen with anencephaly. CDC Archive
Associated spine defects (craniorachischisis). The open head defect may extend down the back. CDC Archive
Other organ differences. Some babies have heart or limb anomalies because early development was disrupted. CDC Archive
Very short survival after birth. Most infants die within hours or days because critical brain tissue is missing. CDC
Severe grief and stress for the family. Early diagnosis gives time for counseling and compassionate planning. (General counseling guidance from obstetric practice.) ACOG
Diagnostic tests
A) Physical exam (after birth)
Head and scalp inspection. The missing skull and exposed area are seen immediately; no special tools are needed. CDC Archive
Gentle palpation of skull edges. Confirms absence of the cranial vault bones (calvaria). CDC Archive
Head-size measurement. Head circumference is extremely small or cannot be measured because the vault is absent. NCBI
Simple neurologic check. Only brainstem-level reflexes may be present; there is no evidence of awareness. New England Journal of Medicine
B) “Manual” bedside assessments (without lab or imaging)
Abdominal palpation in late pregnancy (Leopold maneuvers). Experienced clinicians may feel an abnormally soft or un-ballotable head, prompting urgent ultrasound. (Bedside inference; ultrasound confirms.) NCBI
Fundal-height tracking. Rapid growth from polyhydramnios can raise suspicion and trigger imaging. ScienceDirect
Pelvic exam late in labor (rarely used now). Historically, lack of firm skull plates could be felt; today ultrasound is preferred for diagnosis. NCBI
Newborn reflex testing (e.g., suck/Moro). Reflexes may be weak or absent; if present, they reflect only brainstem function. New England Journal of Medicine
C) Lab and pathological tests
Maternal serum alpha-fetoprotein (MSAFP). A blood test at ~15–20 weeks; very high values strongly suggest an open neural tube defect, and detection for anencephaly is >95% when done correctly. The ObG Project
Amniotic fluid AFP (after amniocentesis). Confirms that AFP is leaking from exposed neural tissue. PMC
Amniotic fluid acetylcholinesterase (AChE). More specific marker for open NTDs when AFP is high. PMC
Chromosomal testing (karyotype or chromosomal microarray) if parents want it. Looks for other chromosome problems; anencephaly is usually not due to aneuploidy, but testing can be part of counseling. ACOG
Targeted genetic studies in research or special cases. Some centers test gene panels (e.g., planar-cell-polarity pathway) to study cause and recurrence risk. PMC
Pathology exam of the fetus/placenta after delivery (with consent). Confirms the anatomic diagnosis and checks for associated anomalies, which helps future-pregnancy counseling. CDC Archive
Important screening note: Cell-free DNA (NIPT) checks chromosomes and does not screen for open neural tube defects; all patients should still be offered a structural ultrasound (and many programs include MSAFP). ACOG
D) Electrodiagnostic tests
Electroencephalogram (EEG) after birth. Shows lack of cortical activity because the cortex is absent; this can document the level of brain function. New England Journal of Medicine
Auditory brainstem response (ABR). Tests brainstem pathways; responses, if present, reflect only brainstem activity and not awareness. Medscape
Fetal or newborn heart-rate monitoring. Used for general care; it does not diagnose anencephaly but is often part of routine obstetric/newborn monitoring. (General practice context.) ACOG
E) Imaging tests
First-trimester transvaginal ultrasound (≈10–14 weeks). Experienced sonologists can detect AEAS features early; modern ultrasound detects almost all anencephaly cases. AJOG+1
Second-trimester anatomy scan (18–22 weeks). Recommended for all pregnancies to look for structural defects; anencephaly is usually unmistakable. ACOG
3D ultrasound. Helps show the missing skull and the shape of the exposed brain tissue and is useful for counseling. PMC
Fetal MRI (selected cases). Clarifies anatomy and associated brain/spine findings when ultrasound views are limited. NCBI
Follow-up ultrasounds during pregnancy. Track polyhydramnios, growth, and any associated defects; critical for planning delivery and supportive care. obgyn.onlinelibrary.wiley.com
Postnatal imaging (rarely needed). The diagnosis is visible at birth; X-ray or MRI may be used only for documentation or research. CDC Archive
Early “acrania” markers on ultrasound (e.g., the “beret” sign). These early signs help predict the sequence toward anencephaly. SpringerLink
Non-pharmacological care
Because anencephaly cannot be cured, “treatment” means accurate diagnosis, compassionate counseling, birth planning, and palliative comfort care for baby and family. Below are evidence-based components you can expect; each is brief and in plain English.
Clear, kind counseling at diagnosis: clinicians explain what anencephaly is, what it means for the baby, and all options, without pressure. This reduces fear, helps informed choices, and supports mental health. ACOG
Multidisciplinary team: maternal-fetal medicine, neonatology, palliative care, social work, spiritual care. Families get consistent answers and support. ACOG
Birth plan (“palliative birth plan”): a written plan for labor, delivery, who will be present, comfort-care steps, photos, and memory-making. This gives parents control and lowers anxiety. Frontiers
Option review (full spectrum): per ACOG, ethically provide the full range of options, including pregnancy termination where legal, expectant management, and palliative newborn care. Respect for the family’s values is central. ACOG
Follow-up ultrasounds: track pregnancy progress and plan timing/place of birth. publications.smfm.org
Delivery planning: vaginal birth is usually safest; cesarean is not recommended unless there is a maternal reason. PMC
Skin-to-skin and family time: once born, parents can hold and spend time with their baby; this is central to memory-making and grief support. ACOG
Comfort positioning and warmth: keep baby warm and quietly held; avoid unnecessary procedures. ACOG
Symptom relief (non-drug): swaddling, gentle mouth care, low-stimulus environment; these lower distress. PMC
Symptom relief (drug, if needed): small, individualized doses of opioids (for air hunger/pain), benzodiazepines (for agitation), and anticholinergics (for secretions) as palliative comfort care. Families are taught that the goal is comfort. Frontiers+1
Lactation support: discuss suppression vs donation options; align with the parent’s wishes. ACOG
Bereavement & memory-making: photos, hand/footprints, naming ceremonies, mementos. Helps long-term healing. ACOG
Sibling & family support: age-appropriate explanations and grief resources for children and relatives. ACOG
Community and faith resources: link to religious/cultural supports if desired. ACOG
Perinatal hospice programs: structured support from diagnosis through aftercare. BioMed Central
Social-work support: help with travel, time off work, financial and logistical needs. ACOG
Ethics consultation (when needed): helps resolve disagreements and protect family values. PubMed
Future-pregnancy planning: review recurrence risk and folate plan (see Prevention). ScienceDirect
Primary-care follow-up for parents: screen for depression, PTSD, complicated grief; connect to counseling. ACOG
Documentation: a clear summary of diagnosis and the family’s preferences to avoid repeating painful conversations. Frontiers
Drug treatments
There are no medicines that treat or reverse anencephaly. Medications are used only for prevention before pregnancy (folic acid) and for comfort care (symptom relief) if a baby is born alive. Below are the most relevant, evidence-based medications in this context, with plain explanations. CDC
Folic acid 400–800 mcg daily (all who could become pregnant): Start before conception and continue through at least the first trimester. This dose lowers the chance of any NTD. It’s in many multivitamins. USPSTF+2CDC+2
High-dose folic acid 4 mg daily (high-risk): If you previously had an NTD-affected pregnancy, or you have certain high-risk conditions/medicines, specialists often advise 4 mg/day, starting ≥3 months before conception and continuing through the first 12 weeks. This reduces recurrence risk. (This higher dose is a separate supplement, not just a prenatal vitamin.) Always follow your clinician’s advice. ACOG+2PMC+2
Comfort-care medicines for newborns (individualized): tiny doses of opioids (e.g., morphine) for air hunger or pain; benzodiazepines for agitation; anticholinergics for secretions; acetaminophen for fever. These do not treat anencephaly; they simply keep the baby comfortable. Frontiers+1
Because there is no disease-modifying drug, providing a list of “20 drugs” would be misleading and unsafe. The safe, evidence-based medications here focus on prevention and comfort. CDC
Dietary molecular supplements
Only folic acid has strong, universal evidence for preventing NTDs. Other nutrients are being studied; some have observational or mechanistic support, but they do not replace folic acid. Always discuss supplements with your clinician.
Folic acid (proven): 400–800 mcg/day for all who could become pregnant; 4 mg/day for high-risk. Function: DNA synthesis and methylation for neural tube closure. Mechanism: supports one-carbon metabolism; corrects low folate status. USPSTF+1
Vitamin B12: Low B12 is linked to higher NTD risk, especially with low folate. Function: works with folate in one-carbon metabolism. Mechanism: supports methylation; low B12 raises homocysteine. (Evidence supports adequacy; formal prevention dosing is not standardized beyond correcting deficiency.) PMC+1
Vitamin B6 & B2 (riboflavin): Important cofactors in one-carbon metabolism; low status has been associated with higher NTD risk in studies. Role: may augment folate pathways; needs more high-quality trials. MDPI
Choline (emerging): Observational studies link better choline status/intake with lower NTD risk; many prenatals lack choline. Function: methyl donor and membrane component. Mechanism: supports neural development and methylation. (Guidelines have not universally adopted choline supplementation for NTD prevention.) PMC+1
Myo-inositol (investigational): Small human pilot (high-risk women) found zero recurrences in the inositol+folate arm vs one in placebo+folate; robust trials are still needed. Function/Mechanism: may reduce “folate-resistant” NTDs via cell-signaling pathways. Only consider in research or with specialist advice. PubMed+1
Multivitamin with folic acid: Ensures a baseline of folate and other cofactors (B12, B6, etc.); associated with NTD risk reduction. New England Journal of Medicine
Dietary folate: Folate-rich foods (leafy greens, legumes) help but usually cannot reach the preventive dose without supplementation. Fortified grains are important where available. CDC
Address iron with clinician: not a direct NTD prevention tool, but standard prenatal iron supports maternal health; combine with folate per guidance. ACOG
Avoiding folate antagonists: not a “supplement,” but a key part of nutrition/medication planning—avoid or replace medicines that impair folate when possible. Lippincott Journals
Overall one-carbon nutrient adequacy: patterns with sufficient folate, B12, B6, B2, choline, and methionine are linked to lower NTD risk in population studies; talk with your clinician about a balanced plan tailored to you. PMC
Immunity-booster / regenerative / stem-cell drugs
No “immunity booster,” “regenerative,” or stem-cell drug can prevent, reverse, or treat anencephaly. Recommending such products would be unsafe and misleading. Ethical care focuses on prevention, accurate diagnosis, and palliative comfort, not unproven therapies. CDC
Surgeries
There is no surgery that can create the missing skull and brain. Care involves obstetric procedures based on the family’s choices and local laws: induction of labor for pregnancy termination where legal, or planned vaginal birth with palliative care. Cesarean section is not recommended for fetal reasons in anencephaly; it’s considered only for maternal indications. JOGC+1
Prevention
Take folic acid 400–800 mcg daily if you could become pregnant (start before conception). USPSTF
If you had a prior NTD pregnancy or are otherwise high-risk, take 4 mg folic acid daily as advised, starting ≥3 months before conception through 12 weeks. ACOG+1
Plan pregnancy when possible: see a clinician before trying, review medicines, optimize nutrition. USPSTF
Tight diabetes control before and during pregnancy. PMC
Reach a healthy weight before conceiving. PMC
Avoid high fevers/hyperthermia (treat fever promptly; be cautious with hot tubs/saunas) in early pregnancy. ScienceDirect
Avoid teratogenic/folate-antagonist drugs (e.g., valproate, methotrexate) if alternatives exist—only under clinician guidance. Lippincott Journals
Use fortified grains (where available) and eat folate- and choline-rich foods (greens, beans, eggs). CDC+1
Space pregnancies to allow time to rebuild nutrient stores and plan medications. USPSTF
Genetic and recurrence counseling after any NTD-affected pregnancy, to personalize your next-pregnancy plan. PMC
When to see a doctor
Before you’re pregnant: to start folic acid, review medicines (especially anti-seizure drugs), and plan diabetes/weight goals. USPSTF+1
As soon as you have a positive test: arrange early prenatal care and first-trimester ultrasound. publications.smfm.org
Any high fever in early pregnancy: treat fever and get assessed. ScienceDirect
If you previously had an NTD pregnancy: you’ll likely need the 4 mg folic acid plan and targeted screening. ACOG
If an ultrasound suggests an anomaly: you should be offered referral to maternal-fetal medicine and perinatal palliative counseling to discuss options and make a birth plan that matches your values. ACOG
What to eat & what to avoid
Eat more:
Folate-rich foods (spinach, lentils, black beans, citrus) plus a folic-acid supplement.
Choline-rich foods (eggs, lean meats, soy) to support neural development.
Balanced meals with whole grains (fortified where available), fruit, vegetables, legumes, nuts, and adequate protein. CDC+1
Avoid/limit:
Alcohol, tobacco, and recreational drugs (raise overall birth-defect and pregnancy risks).
Very high vitamin A/retinoid supplements unless prescribed (teratogenic).
Hot tubs/saunas that raise core temperature early in pregnancy.
Unapproved herbal products claiming to “boost immunity” or “prevent defects.” Talk with your clinician before taking any supplement. Verywell Family+1
FAQs
Is there any cure? No. Anencephaly is not reversible. Care focuses on prevention and compassionate support. CDC
Can surgery fix it? No. Missing skull and brain cannot be surgically created. JOGC
How early can it be seen? Often by late first trimester; almost always by the 18–22-week scan. publications.smfm.org
What is the usual outcome? Miscarriage, stillbirth, or death within hours–days after birth. CDC
What are my options after diagnosis? Per ACOG: full spectrum—pregnancy termination where legal, or expectant management with a palliative birth plan. ACOG
Will my baby suffer? Teams focus on comfort (warmth, holding, gentle symptom relief). ACOG
Can my baby donate organs? Rare and highly regulated; discuss locally. Some tissues (e.g., corneas) may be possible depending on laws and timing. (Discuss with the care team.) ACOG
What is my chance of this happening again? Baseline recurrence risk ~2–3% without high-dose folate; high-dose folate lowers recurrence. ScienceDirect+1
How long should I take folic acid? Ideally start ≥1–3 months before conception and continue through the first 12 weeks; for general prevention, continue daily if you could become pregnant. USPSTF+1
Is 4 mg folic acid safe? It’s recommended for high-risk women under clinician supervision; use a separate 4-mg tablet in addition to a prenatal. ACOG
Does folic acid cause autism, twins, or cancer? No credible evidence of such harms; large reviews show benefit without these harms. JAMA Network
Do I need extra B12? Ensure adequacy, especially if you eat little/no animal foods or have absorption issues; work with your clinician to check levels. Genome.gov
What about inositol? Promising in small, high-risk studies but not standard; ask a specialist before using. PubMed
What delivery method is best? Usually vaginal birth; cesarean only for maternal indications. PMC
Who can help us plan and cope? Perinatal palliative care teams guide medical choices, birth planning, memory-making, and bereavement support. ACOG
Disclaimer: Each person’s journey is unique, treatment plan, life style, food habit, hormonal condition, immune system, chronic disease condition, geological location, weather and previous medical history is also unique. So always seek the best advice from a qualified medical professional or health care provider before trying any treatments to ensure to find out the best plan for you. This guide is for general information and educational purposes only. Regular check-ups and awareness can help to manage and prevent complications associated with these diseases conditions. If you or someone are suffering from this disease condition bookmark this website or share with someone who might find it useful! Boost your knowledge and stay ahead in your health journey. We always try to ensure that the content is regularly updated to reflect the latest medical research and treatment options. Thank you for giving your valuable time to read the article.
The article is written by Team RxHarun and reviewed by the Rx Editorial Board Members
Last Updated: September 17, 2025.
