Comparison of Amniotic Fluid Alpha-Fetoprotein and Gel-Acetylcholinesterase Tests With Fetal Blood Contamination

Abstract

The addition of 5% fetal serum, equivalent to 1.5 ml fetal blood in 20 ml of amniotic fluid, can result in a false positive amniotic fluid AFP test. The qualitative ACHE test requires the addition of more than 3 ml of fetal blood to be abnormal. We recom mend a repeat amniocentesis whenever both tests are positive despite the presence of fetal blood, but this may be avoided when the presence of fetal blood appears to explain a slightly elevated AFP (2+3 SD<+5 SD) and the AChE and sonogram are normal. (Thai J Obstet Gynaecol 1989; 1 :1-5)