Acrania, Anencephaly, and Encephelocele – Fetal Development

Posted On: August 9, 2021 By Nathan D. Fox, MD

Acrania, Anencephaly and Encephalocele are birth defects classified as neural tube defects that occur early in pregnancy. Neural tube defects (NTDs) occur when the neural tube, a structure that folds and closes within the first month of pregnancy, does not close completely or correctly.

Neural tube defects are the second most common congenital anomaly in the United States, second to cardiac malformations, which are associated with substantial morbidity and mortality.

The majority of NTDs are isolated malformations that have many risk factors both genetically and in the environment. However, there is a higher prevalence of karyotypic (genetic) abnormalities among fetuses with NTDs, especially when other congenital abnormalities are found. Trisomy 18 is the most common genetic abnormality associated with NTDs. For this reason, fetal karyotyping can help with diagnostic evaluation and recurrence risk counseling.

What is Acrania?

Acrania refers to the absence of a fetal skull with freely exposed brain tissue to amniotic fluid. Acrania often results in anencephaly, and some believe it is a precursor to all cases of anencephaly. Both can be seen on ultrasound in the first trimester. Unfortunately, the prognosis is uniformly dismal as these are lethal disorders.

What is Anencephaly?

Anencephaly refers to the absence of the upper portion of the fetal brain. The remaining parts of the brain are exposed, not covered by bone or skin. This NTD affects one out of every 4,600 pregnancies in the United States and is a fatal condition.


Encephalocele is an NTD where there is a defect in the fetal skull allowing a portion of the fetal brain to protrude through the skull. This can result in a small or large protrusion, and prognosis depends on the size of the defect as well as what area(s) of the brain are affected. However, there is typically significant neurologic impairment in most cases of encephalocele. Encephalocele occurs sporadically and affects about one in every 10,000 births. There are additional syndromes associated with this disorder as well, including Meckel-Gruber.

Risk Factors for Neural Tube Defects

Anyone can have a baby that develops an NTD, although there are many conditions that increase the risk of having an NTD. These include:

  • Previous NTD
  • Family history of NTD
  • Obesity
  • Diabetes
  • Use of certain anti-seizure medications

Women with the highest risk are those with a family or personal history of NTDs.

If you’re at risk for an NTD, create a treatment plan with your obstetrician or maternal fetal medicine specialist, including careful monitoring throughout pregnancy, as well as folic acid supplementation before conception and throughout the first trimester.

Diagnosing NTDs

Neural tube disorders such as encephalocele and anencephaly can be detected during an ultrasound imaging appointment.

How to Treat Encephalocele

In cases in which encephalocele is not lethal, there are surgeries to treat the condition. These procedures need to be performed very shortly after birth, which is why it’s always better to know about these conditions through ultrasound imaging so you can create a plan for delivery. Whether surgery (or surgeries) can correct the condition or not, babies born with encephalocele may have neurological disorders such as:

  • Developmental delay
  • Complete muscle weakness or lack of muscle coordination
  • Vision problems
  • Intellectual disability
  • Seizures

Other NTDs, such as anencephaly, are not treatable and are fatal often within a few hours after delivery.

Prevention of NTDs

Folic acid supplements and dietary fortification (including more micronutrients in food) have been shown to decrease the occurrence and recurrence of NTDs. NTD recurrence rate is approximately 2-5%, which is why previous pregnancy with NTD is a key risk factor for the defect. The American College of Obstetricians and Gynecologists, the Centers for Disease Control, and the American Academy of Pediatrics recommend that women with a previously affected child take 4 mg of folic acid per day (ten times the dose recommended to all pregnant women) beginning at least one month before conception and continuing through the first trimester. Pregnancies supplemented with folic acid had a 72% reduction of NTD recurrence.

Where to Find Folic Acid in Your Diet

Although most women at risk for neural tube disorders can take folic acid supplements, others may opt for introducing it through their diet. Foods that are high in folic acid include:

  • Bread
  • Cereal
  • Pasta
  • Flour
  • Corn meal

In particular, look for products that say “fortified” or “enriched,” as these are often terms used to refer to added folic acid.

The United States grows grains that are enriched in folic acid, which has contributed to a national decline in incidences of anencephaly since the practice began. However, for those at high risk for NTDs, increasing the intake of folic acid is still recommended.

Your Partner in Maternal Fetal Health

The expert obstetricians and gynecologists at Maternal Fetal Medicine Associates are here every step of the way to ensure that, when it’s time, you deliver a healthy baby in a safe way. From pre-conception counseling all the way through to delivery, we’ll monitor your progress and adjust your care accordingly.

To learn more about NTDs, including acrania, anencephaly, and encephalocele, don’t hesitate to contact Maternal Fetal Medicine Associates today. We’ll describe the risks, diagnosis, and treatment options you can expect so you aren’t left in the dark with your obstetrical care.

Carnegie Imaging for Women blogs are intended for educational purposes only and do not replace certified professional care. Medical conditions vary and change frequently. Please ask your doctor any questions you may have regarding your condition to receive a proper diagnosis or risk analysis. Thank you!

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