The vitamin E-binding protein afamin increases in maternal serum during pregnancy

Afamin is a liver-derived plasma glycoprotein with vitamin E-binding properties and a putative function in fertility. This study evaluated serum afamin concentrations during and postpartum to uncomplicated pregnancies and investigated a potential association between afamin concentrations and pregnancy outcome. Afamin serum concentrations were measured in women with uncomplicated pregnancies in a retrospective cohort (n=466) at different gestational ages and a prospective observational study (n=76) in the first, second and third trimester. Furthermore, afamin was determined in the first trimester in a cross-sectional pilot study including women with preeclampsia (PE), pregnancy-induced hypertension (PIH) and women without pregnancy complications (n=13 each). Finally, expression of afamin was investigated in human placental tissue by RT-PCR and immunohistochemistry. Afamin concentrations increased linearly almost two-fold during pregnancy in both retrospective and prospective studies in women without pregnancy complications with median afamin serum concentrations of 61.9mg/l, 79.6mg/l, and 98.6mg/l in the first, second, and third trimester, respectively. After delivery, median afamin concentrations decreased to baseline values of 54.6mg/l. In the pilot study with pregnancy complications, women with PE displayed significantly higher median afamin concentrations than did women with uncomplicated pregnancy (70.0mg/l vs. 55.4mg/l, P=0.007). Expression analyses revealed no placental afamin expression at either mRNA or protein level in uncomplicated pregnancy. A linear increase in the maternally expressed glycoprotein afamin during pregnancy may serve as basic reference for subsequent investigations of afamin in pregnancy-related disorders. •Serum afamin concentrations during and postpartum to uncomplicated pregnancies were evaluated.•Analysis of afamin in cross-sectional pilot study in patients with pregnancy complications.•Afamin linearly increased two-fold in women with uncomplicated pregnancies.•First trimester serum values of afamin were significantly higher in women with pregnancy complications.•Lacking placental afamin expression suggests maternal origin of circulating afamin.