A monoclonal antibody based solid-phase enzyme-binding assay to measure levels of placental alkaline phosphatase in serum of women during pregnancy.

Monoclonal antibodies raised against highly purified placental alkaline phosphatase (PALP) reacted specifically with PALP and were found not to cross-react with the liver, kidney and intestinal enzymes. One of these antibodies (AP-3) was selected to develop an enzyme-binding assay to measure levels of PALP in the sera of 11 women throughout pregnancy. PALP activity rose sharply after 28 weeks of gestation reaching a peak at delivery followed by an immediate drop within 4 days to values approaching non-pregnant levels. The potential of using this assay as an index of placental function to monitor progress of a pregnancy is discussed.