Trefoil factors (TFF1-3) are 7-12 kDa peptides secreted by mucosal surfaces, with changing levels of expression reflected in serum concentrations. The genes for the peptides are located on chromosome 21, the chromosome duplicated in trisomy 21. We studied the levels of circulating TFFs in pregnant women carrying trisomy 21 foetuses and in women with normal pregnancies, throughout pregnancy and postpartum.