• Measurement of amniotic fluid AFP
• Detection of AChE
• The reflex to fetal hemoglobin (Hb F) will be used, if necessary, to ascertain false elevations of amniotic fluid AFP due to contamination with fetal blood

Analysis of midtrimester amniotic fluid for detection of open neural tube and ventral wall defects

AChE false-positive and false-negative results are more frequent at gestational ages of less than 13 weeks.

• The patient should have undergone ultrasound studies to verify fetal viability, detect multiple gestation, confirm gestational age, localize placenta, and detect fetal and uterine pathology
• Patient's gestational age must be at least 12 weeks for interpretation of α-fetoprotein
• Optimal gestational age for detection of AChE is 14 - 18 weeks

Sterile vial/container

Do not use urine containers or tubes with rubber stoppers as rubber is toxic to amniocytes

Avoid contamination of amniotic fluid with maternal or fetal blood. As little as one drop of fetal blood can cause false-positive results during assay of amniotic fluid.

Unspun and supernatant amniotic fluid is acceptable

Sterile vial/container

• Gestational age by ultrasound and/or last menstrual period (LMP)

Ambient (preferred) - 7days

Refrigerated - NO

Frozen - NO

• specimen found not to be amniotic fluid
• gross contamination of amniotic fluid with maternal or fetal blood
• quantity not sufficient for analysis

Chemiluminescent immunoassay

Acrylamide gel electrophoresis

Isoelectric focusing

AFP - An interpretive report will be provided

AChE - Negative