“…PAP is synthesized in the syncytiotrophoblast and reaches the maternal circulation early in the first trimester (Okamoto et al, 1990). An association between elevated activity of neutrophil PAP and trisomy 21 was reported in affected individuals (Lennox et al, 1962;Tangheroni et al, 1971;Grozdea et al, 1991), as well as in mothers with presently ongoing or previous Down syndrome pregnancies (Grozdea et al, 1983;Vergnes et al, 1988;Grozdea et al, 1988;Brisson-Lougarre et al, 1991;Denier et al, 1996). An increase in PAP activity was also described in maternal serum in the second trimester of affected pregnancies (Ind et al, 1994;Denier et al, 1996).…”