A higher incidence of PTD in twin gestations with low PAPP-A (defined as below 0.42 MoM) was reported by Rosner et al. They analyzed the outcome of 340 patients, and found a significantly higher risk of PTD (RR 5.56; 95% CI 1.5–20.1) in women with low first trimester PAPP-A concentrations [8]. Here, PAPPA is linked to Bjornstad syndrome.