Screening

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

Antenatal quadruple screen

The quadruple screen includes AFP (alpha-fetoprotein), hCG (human chorionic gonadotrophin), uE3 (unconjugated estriol), and inhibin A. These studies of maternal serum are offered to all pregnant women between 15 and 22 weeks' gestation.[99] A mathematical calculation involving the levels of these four substances and considerations of maternal age, weight, race, and diabetic status are used to determine risk. The quadruple screen can detect about 75% to 80% of pregnancies affected by spina bifida and nearly 95% of those with anencephaly.[75] Availability of this test may vary in some countries.

Antenatal ultrasound

Ultrasound following an elevated 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.[60][61][76][77]​ Three-dimensional ultrasound using multiplanar views can achieve diagnostic accuracy within 1 vertebral body in around 80% of patients.[76][77][100]

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.[61]

Care should be exercised in recommending antenatal surgery when the ventricles are 15 mm or larger, because antenatal surgery does not appear to improve outcome in this group.[101]

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