Samples collection and angiogenic factors measurement
At admission, a 5 ml peripheral maternal blood sample was obtained. Serum was separated by centrifugation at 2000 g for 10 min at room temperature, and samples were immediately stored at -80ÂșC until assayed at an independent laboratory. Clinicians and researchers were unaware of the angiogenic factor levels as they were measured after delivery on stored samples.
Maternal serum concentration of sFlt-1 and PlGF was determined by the fully automated Elecsys assays for sFlt-1 and PlGF on an electrochemiluminescence immunoassay platform (Cobas analyzers, Roche Diagnostics). In all the kits, the intra-assay precision was <4% for both assays and the inter-assay precision was 2.3-5.6% and 2.4-4.6% for sFlt-1 and PlGF assays respectively.