Screening for trisomies 21 and 18 with maternal serum placental isoferritin p43 component

A component of placental isoferritin, p43, is an immuno-regulatory protein associated with suppression of the immune system. Maternal serum p43 levels increase throughout pregnancy and low serum levels have been associated with various pathological pregnancies, particularly those with a defect of placentation. We measured maternal serum p43 retrospectively in banked samples from 42 Down syndrome, 20 Edwards' syndrome and 281 unaffected pregnancies to assess its screening potential in both the first and second trimesters. The median maternal serum p43 level in Down syndrome was 1.58 times higher than that in the unaffected pregnancies (p=0.01, two-tail). The median level was slightly, but not significantly, reduced in Edwards' syndrome. Statistical modelling, including parameters for alpha-fetoprotein, free beta-human chorionic gonadotrophin, and unconjugated oestriol suggested that it might have a role in Down syndrome screening when combined with two or three of these markers. Larger scale studies are now needed.