The development of the human brain is a remarkably complex process that begins in the very first weeks of pregnancy and demands an extraordinarily delicate balance. Disruptions to this process can give rise to severe congenital anomalies that profoundly affect the structure of the baby while still in the womb. Anencephaly is one of the most well-known and most serious of these anomalies — a neural tube defect characterized by the failure of the brain and a large portion of the skull bones to develop at all. Both medically and ethically significant, it remains a condition that warrants careful understanding.
What Exactly Is Anencephaly?
The word anencephaly is derived from the Greek “an” (without) and “enkephalos” (brain), meaning, quite literally, “without a brain.” Medically defined, it is a severe congenital anomaly in which the upper portions of the brain — the cerebrum and most of the cerebellum — along with the skull bones that would normally cover these regions, fail to develop.
In normal development, a structure called the neural tube closes at around the 28th day of gestation and subsequently transforms into the brain and spinal cord. In anencephaly, this closure fails to occur at the uppermost end of the neural tube — the cephalic end. As a result, the cerebral cortex either does not form at all or develops into a primitive, non-functional mass of tissue; the skull bones and scalp are unable to develop in a way that would cover this region.
How Common Is It?
Anencephaly occurs in approximately 1 in every 1,000 to 10,000 live births. This rate varies considerably depending on geography, dietary habits, and genetic factors. It is well established that incidence rises markedly in regions where folate consumption is low.
Female fetuses are reported to be affected approximately three to four times more often than males. It is also known that a mother who has previously given birth to an anencephalic baby carries an elevated risk of recurrence in subsequent pregnancies.
Why Does It Occur? What Are the Risk Factors?
Anencephaly does not have a single cause; it has a multifactorial etiology, meaning that both genetic predisposition and environmental factors play a role in combination.
Folic Acid Deficiency: This is the most significant and most preventable risk factor identified to date. Inadequate folic acid intake in the period before conception and during the early weeks of pregnancy directly disrupts the neural tube closure process. Large-scale population studies have demonstrated that adequate folic acid supplementation reduces the risk of neural tube defects by 50 to 70 percent.
Genetic Factors: Certain gene mutations and chromosomal anomalies can increase the risk of anencephaly. MTHFR gene variants in particular affect folic acid metabolism and indirectly elevate this risk.
Maternal Diabetes: The presence of poorly controlled type 1 or type 2 diabetes in the expectant mother constitutes a risk factor for neural tube defects.
Hyperthermia Exposure: There is evidence that situations which significantly raise body temperature during the early weeks of pregnancy — such as high fever, prolonged hot tub use, or sauna — are associated with increased risk.
Certain Medications: Antiepileptic drugs such as valproic acid, when used during the first weeks of pregnancy, are among the medications known to increase the risk of neural tube defects.
Obesity: Obesity in the expectant mother has also been identified as an independent risk factor.
Clinical Presentation: The Baby’s Appearance and Physiological State
At birth, babies with anencephaly typically lack the portion of the skull that would normally contain the upper brain regions, or have only a rudimentary structure in its place. The brain tissue is generally exposed, unprotected by any covering membrane.
These babies may show signs of life at birth — heartbeat and respiratory function can be partially sustained by the primitive centers at the level of the brainstem. However, conscious life is not possible in the absence of the cerebral cortex; conscious responses to pain, sound, light, and other stimuli cannot be generated.
The vast majority of anencephalic babies die within hours or days of birth. In very exceptional circumstances, this period may extend to a few weeks.
How Is the Diagnosis Made?
Prenatal Ultrasonography: Anencephaly is a condition that can be identified with a high degree of accuracy while the baby is still in the womb. The characteristic appearance can be detected during routine obstetric ultrasonography — in particular during the first trimester screening performed between 11 and 14 weeks of gestation. The absence of the skull bones and the failure to visualize brain tissue largely confirm the diagnosis.
Maternal Serum AFP Test: A markedly elevated level of alpha-fetoprotein (AFP) in the mother’s blood is an important biochemical finding pointing to neural tube defects. This test is used in a complementary role alongside ultrasound findings.
Amniocentesis: In cases of diagnostic uncertainty, a sample of amniotic fluid can be used for both biochemical analysis and genetic karyotyping.
MRI: In cases requiring advanced imaging, fetal MRI offers the opportunity to evaluate the extent of the brain anomaly in greater detail.
Compatibility with Life
Anencephaly is a lethal anomaly — one that is incompatible with life. This is one of its most grave and ethically challenging aspects. When the diagnosis is made early in pregnancy, families are guided through a comprehensive counseling process covering the options of termination of pregnancy, continuing the pregnancy to term, or pursuing palliative care after birth.
Some families choose to continue the pregnancy in accordance with their religious, cultural, or personal beliefs. In this case, comfort care for the baby after delivery — pain management, warmth, and time with the family — is placed at the forefront.
Ethical Dimensions
Anencephaly is one of the most debated topics in medical ethics. The question of organ donation from anencephalic babies in particular has attracted intense attention over decades within the medical community, bioethics circles, and the legal domain.
Some ethical viewpoints argue that these babies lack the capacity for consciousness and that the presence of functional brain tissue is debatable, and therefore advocate for organ donation to be permitted. On the other hand, whether brain death criteria can be fully applied to anencephalic babies — and the legal framework surrounding this question — varies enormously from country to country. For this reason, each case must be evaluated individually within the framework of applicable laws and institutional ethics committees.
Is Prevention Possible?
While the complete prevention of anencephaly is not currently possible, the risk can be significantly reduced with appropriate measures.
Folic Acid Supplementation: Health authorities worldwide recommend that women of childbearing age begin taking 400 to 800 micrograms of folic acid daily at least one to three months before planning a pregnancy, and continue this supplementation throughout the first trimester. In women who have previously given birth to a baby with a neural tube defect, the dose may be increased to 4,000 micrograms.
Management of Chronic Conditions: Effectively controlling diabetes and other chronic diseases before conception makes a meaningful contribution to risk reduction.
Medication Review: Medications used to treat conditions such as epilepsy that carry a risk of neural tube defects should be evaluated before pregnancy, and alternatives should be considered where possible.
Avoiding Excessive Heat: Prolonged hot tub or sauna use during the early weeks of pregnancy should be avoided.
What Distinguishes Anencephaly from Other Neural Tube Defects?
Neural tube defects form a spectrum and can manifest in a variety of forms. Spina bifida (failure of the spinal canal to close), encephalocele (herniation of brain tissue through the skull), and iniencephaly (a combination of severe head and neck anomalies) are other important entities within this spectrum.
Anencephaly occupies the most severe end of this spectrum. Unlike spina bifida — in which the brain is generally preserved and many patients can survive for an extended period — the absence of the cerebral cortex in anencephaly means that compatibility with life is not possible.
Family Support and Counseling
A diagnosis of anencephaly is devastating news for any family. At this stage, the family needs not only medical information but also psychological support, genetic counseling, and professional guidance through the grieving process.
Genetic counseling is of particular importance for assessing the risk in subsequent pregnancies and planning preventive measures. An experienced perinatology team should keep the family informed at every stage of the process and ensure they are never left to face their decisions alone.
Conclusion: A Painful Reality, a Powerful Preventive Measure
Anencephaly is a severe congenital anomaly that even modern medicine cannot render compatible with life. Yet the fact that a significant proportion of cases are preventable — through adequate folic acid intake and informed pregnancy planning — underscores just how life-saving public awareness can be.
For every woman considering pregnancy, consulting an obstetrician and gynecologist on this matter and beginning folic acid supplementation in a timely manner is one of the most valuable steps that can be taken to eliminate one of the most significant obstacles standing between a planned pregnancy and a healthy child.
Prof. Dr. Mehmet Şenoğlu Neurosurgeon, İzmir
Note: This article is intended for informational purposes only. Please consult a qualified physician for diagnosis and treatment.