Alpha-fetoprotein (AFP) levels in human maternal serum were elevated in 14 patients when measured by a radioimmunoassay. In 8 patients the elveated serum levels of AFP correlated with increased concentration of AFP in amiotic fluid and were diagnostic of fetal defects. The elevated AFP levels in the remaining 6 patients were shown to be the result of fetomaternal transfusion from either amniocentesis or natural causes. Serum samples drawn after amniocentesis through an anterior placenta may show false-positive elevations. The use of both maternal serum and amniotic fluid samples in pregnancies at high risk for neural tube defects can decrease the risk of diagnostic errors due to mistakes in gestational datind and may increase the diagnostic sensitivity of amniocentesis.
PIP: 14/150 patients studied over a 2-year span had elevated serum alpha fetoprotein (AFP) in the course of pregnancy; fetal abnormality or a source of fetomaternal transfusion was present in each case. The fetomaternal transfusions generally resulted from amniocentesis through an anterior placenta. In 4 cases, fetal demise with fetal maceration occurred. In 3 of these, amniotic fluid AFP concentrations were 10 times the normal for that gestational week. Sequential serum AFP rose to nearly twice the initial value in 1-3 weeks. In 3 cases, the fetuses had neural tube defects, and in each case both amniotic fluid and maternal serum AFP were elevated. In 5 cases with initially false positive serum elevations not accompanied by elevated amniotic fluid AFP, fetomaternal transfusion resulting from amniocentesis was the cause; in all, 7 cases of maternal serum elevation secondary to fetomaternal transfusion were recorded. Analyzing both maternal serum and amniotic fluid samples in pregnancies at high risk for neural tube defects can decrease diagnostic errors caused by mistakes in gestational dating and may increase the diagnostic sensitivity of amniocentesis.