Maternal serum concentrations of pregnancy associated placental protein A and pregnancy specific {beta}-1-glycoprotein in multifetal pregnancies before and after fetal reduction

Placental function in multifetal pregnancies before and afterembryo reduction was investigated by measuring maternal serumconcentrations of pregnancy associated placental protein-A (PAPP-A)and pregnancy specific -1-glycoprotein (SP-1). Three groupsof pregnant women were studied following assisted reproduction;groups 1 and 2, were 12 singleton and 12 twin pregnancies respectively,and group 3 comprised 12 women with multifetal pregnancies undergoingembryo reduction. PAPP-A and SP-1 were measured serially at8–21 weeks gestation. In all pregnancies, maternal serumPAPP-A and SP-1 increased with gestation. In twin pregnanciesthe mean concentrations of SP-1 were significantly higher thanin singletons at all gestations, whereas for PAPP-A, concentrationswere similar between these groups. In multifetal pregnanciesbefore embryo reduction, the serum concentrations of both proteinswere significantly higher than in twin pregnancies. Followingreduction, the concentrations of PAPP-A remained significantlyhigher than for twins throughout, whereas the concentrationsof SP-1 gradually converged towards those of twins; by 19 weeksthere was no difference between the means of the two groups.These findings suggest that circulating concentrations of SP-1reflect total placenta mass, which is proportional to the numberof live fetuses, whereas the pattern of PAPP-A changes suggeststhat this protein is produced by the placenta, decidua and othertissues.