A case of false positive amniotic acetylcholinesterase in a normal pregnancy.

Kim, Youn Hee; Lee, Jee Hyun; Moon, Hee Bong; Oh, Jun Hwan; Lee, Gui Se Ra; Yi, Chong Seung; Shin, Jong Chul; Kim, Soo Pyung

Case Report

Korean Journal of Obstetrics & Gynecology 2002;45(2):353-356.
Published online February 1, 2002.

A case of false positive amniotic acetylcholinesterase in a normal pregnancy.

Youn Hee Kim, Jee Hyun Lee, Hee Bong Moon, Jun Hwan Oh, Gui Se Ra Lee, Chong Seung Yi, Jong Chul Shin, Soo Pyung Kim

Department of Obstetrics and Gynecology, Catholic University Medical College, Seoul, Korea.

Abstract

Maternal serum alpha-fetoprotein (AFP) has been used for a long time for the prenatal diagnosis of neural tube defects in women at midtrimester of gestation. But AFP is elevated not only in cases of neural tube defects, but also in fetus with congenital nephrosis, abdominal wall defects, fetal demise, low birth weight or simply erroneously calculated gestational age. So, when maternal serum AFP is increased, gestational age of the fetus must be re-evaluated and targeted ultrasonographic evaluation is indicated to rule out neural tube defects. If NTDs are suspected or ultrasound is non-diagnostic, amniotic fluid AFP are measured and when AF-AFP is elevated, the presence or absence of acetylcholinesterase should be evaluated. The detection rate of open neural tube defects using amniotic acetylcholiesterase is reported to be as high as 96 to 99% with a 0.06% and 0.14% of false positive rate in amniotic fluids non-contaminated and contaminated by blood, respectively. We report a case with elevated mid-trimester MS-AFP, AF-AFP and positive amniotic acetylcholin-esterase, but in which repeated sonographic findings were normal, and result in delivery of a heathy baby without anomalies.

Key Words: AF-AFP, open neural tube defect, Acetylcholinesterase