A multidirectional sonographic approach to elevated amniotic alpha-fetoprotein or positive acetylcholinesterase

To evaluate the combined transvaginal and transumbilical ultrasonographic approach in cases of elevated amniotic fluid (AF) alpha-fetoprotein (AFP) and/or acetylcholinesterase in the second trimester.

Nine pregnant women with normal sonographic results were referred because of elevated AF AFP and/or acetylcholinesterase and screened using a transvaginal and transumbilical 6.5-MHz ultrasound transducer. All women were at 17-21 weeks' gestation. The fetal skull and the vertebral column were scanned in both perpendicular and tangential planes for maximal exploitation of the axial resolution of the transducer, in both directions and in two to three planes.

Despite increased AF AFP and/or present acetylcholinesterase, no fetal malformation was detected in any of the nine cases. Open neural tube defects were not detected by the diagnostic technique. All nine women were delivered of term healthy neonates without malformations.

Our preliminary data suggest that targeted sonographic screening combining transvaginal and transumbilical approaches may reliably rule out an open neural tube defect larger than 0.3 mm. This may influence the decision-making process when termination of pregnancy is considered in cases of high AF AFP and/or positive acetylcholinesterase.