Prenatal diagnosis of the Meckel syndrome.

Sixteen pregnancies of 12 women with a previous child affected with the Meckel syndrome were monitored by ultrasonic scanning and amniotic fluid alpha-fetoprotein (AFP) assay. Second-trimester AFP testing in 14 pregnancies detected 1 of 2 affected fetuses, and was normal in all 12 pregnancies in which the child was normal. It is concluded that measurement of amniotic fluid AFP is helpful for Meckel syndrome only when there is an associated open neural tube defect. The importance of extremely careful ultrasonography is emphasized.