Screening

Most neural tube defects are diagnosed prenatally by screening methods that are offered to all pregnant women during the second trimester.

Prenatal triple or quadruple screen

The triple screen includes AFP (alpha-fetoprotein), hCG (human chorionic gonadotropin), and uE3 (unconjugated estriol). The quadruple screen also includes inhibin A. These studies of maternal serum are offered to all pregnant women between 15 and 20 weeks' gestation.[94] A mathematical calculation involving the levels of these 3 or 4 substances and considerations of maternal age, weight, race, and diabetic status are used to determine risk. Both the triple and the quadruple screen can detect about 75% to 80% of pregnancies affected by spina bifida and nearly 95% of those with anencephaly.[72]

Prenatal ultrasound

Ultrasound following an elevated triple/quadruple screen excludes an open neural tube defect with a high degree of confidence, although interpretation requires a great deal of expertise, and false-negative studies have been reported.[64]​[73][74]​​​​​​ Three-dimensional ultrasound using multiplanar views can achieve diagnostic accuracy within 1 vertebral body in around 80% of patients.[73][74][95]

First-trimester ultrasound screening for neural tube defects is recommended if the risk of a neural tube defect is high based on family and/or maternal history.​[64]

Care should be exercised in recommending prenatal surgery when the ventricles are 15 mm or larger, because prenatal surgery does not appear to improve outcome in this group.[96]

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