May 30, 2024

Anencephaly : A severe Birth defect

  • June 17, 2010
  • 3 min read
Anencephaly : A severe Birth defect

Anencephaly- Clinical features, pregnancy diagnosis, prevention and treatment.

Severe Neural Tube Defect

Spina Bifida and anencephaly are most common Neural Tube Defect ( NTD) followed by encephalocele.  Anencephaly is a severe form of NTD, with 100% mortality. The baby is either born dead or is unfit for survival.
Anencephaly is a congenital birth defect (from the Latin congenitus, “born with”)

Incidence Of Anencephaly: 1 in 1000 children ( world statistics, exact for Nepal is not available). In USA data is 1 in 150,000 to 200,000 babies born each year are anancephalic .

Cause Of Anencephaly:

  • The anomaly results from deficient development development of the vault of skull and brain tissue due to incomplete closure of the Rostral Neuropores.

Clinical Features

  • The facial portion is present. Infants with this disorder are born without a scalp or cerebellum. Their meninges, both hemispheres of the brain and the vault of the cranium/skull are also missing, though they usually do have part of the brain stem. The remaining brain tissue is protected only by a thin membrane.
  • About ¼ of anencephalic babies die at birth; those who survive have a life expectancy of a few hours or days
  • A baby born with anencephaly is usually blind, deaf, unconscious, and unable to feel pain. Although some  may be born with a main brain stem, the lack of a functioning cerebrum permanently rules out the possibility gaining consciousness.
  • Reflex actions such as breathing and responses to sound or touch occur.
  • The pituitary gland is often absent or if present is hypoplastic. Secondary to absence of stimulation in absence of ACTH , pituitary glands are also atrophied.

Risk Factors:

  • Previous history of birth of infant with NTD
  • 70 % of the cases are female .
  • It is most common in first birth and among young and elderly mothers.
  • Genetic and environmental factors are suspected to be involved.

Diagnosis Of Anencephaly:

  1. In the first half of pregnancy, the diagnosis is made by elevated Alpha-fetoprotein in Amniotic fluid and confirmed by sonography. The findings around 13 weeks gestation are:- Absence of Cranial vault, Angiomatous brain tissue.
  2. In later half of pregnancy, the diagnosis may be a problem.  Hydraminous and inability to palpate fetal head can arouse suspicion.
  3. Face presentation is revealed by internal examination ( per vaginum).
  4. Confirmation  is done by USG or X ray.


  1. Hydramnios
  2. Malpresentation – face or breech
  3. Premature labour
  4. Tendency to post-maturity
  5. Shoulder dystocia
  6. Obstructed labour – if head and shoulder present (compound) due to short neck


  • If diagnosed before 20 weeks of pregnancy: Termination of Pregnancy is done
  • If Diagnosed Late:  PGE2 (Cerviprim gel can be used to to terminated the pregnancy as Uterus is usually resistant to Oxytocin.
  • If Diagnosed During labor- The labor is likely to be prolonged. For Shoulder dystocia- Cleidotomy should be done. ( Cutting the clavicle bones)

Prevention Of Anencephaly:

  1. Pre-pregnancy Counselling is important.
  2. Folic Acid supplementation 4 weeks before the conception to 12 of pregnancy  has reduced the incidence of NTD significantly.    A dose of 4 mg daily is recommended.
  3. Regular follow up visits Antenatal.
  4. Mothers on drug ( Antiepileptics) should consult the doctor.


Source : DC Dutta Obstetrics book, Wikipedia, .

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