Analysis of midtrimester amniotic fluid for detection of open neural tube defects and ventral wall defects
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.
Do NOT use urine containers or tubes with rubber stoppers; rubber is toxic to amniocytes.
Gestational age by ultrasound and/or last menstrual period (LMP)