Role of ultrasound and informed consent in the evaluation of elevated maternal serum alpha-fetoprotein.

Informed consent of medical procedures should include a discussion of both the risk of the procedure and the probability of the malady in question. Many centers in the United States currently recommend amniocentesis for all women with elevated levels of maternal serum alpha-fetoprotein (MSAFP) unexplained by targeted ultrasound examination. Prospective clinical data from our unit support the use of an algorithm that provides for a 90% reduction of the predicted risk of neural tube defect from MSAFP alone. The predicted risk is revised only if the ultrasound shows normal fetal cranial size and shape, normal ventricular size, normal posterior fossa anatomy, and normal spinal anatomy. Preliminary results supported this approach with no reduction in sensitivity, while substantially reducing the need for invasive testing. The additional experience reported here of 20,211 patients resulted in 451 ultrasound examinations for an elevated MSAFP, but only 54 amniocenteses. During this period, nine open neural tube defects were detected among patients with elevated MSAFP using ultrasound; none was missed. All fetuses with defects had ultrasound findings of cranial and intracranial changes first reported by Campbell. These data support the premise that, prior to amniocentesis, informed consent should include discussion of the ultrasound evaluation.