[1] UNIV BOLOGNA, INST NEUROL SURG, VIA U FOSCOLO 7 PORTA SARAGOZZA, I-40123 BOLOGNA, ITALY
[2] UNIV BOLOGNA, DEPT STAT SCI, I-40123 BOLOGNA, ITALY
[3] UNIV BOLOGNA, INST NEONATOL, I-40123 BOLOGNA, ITALY
[4] UNIV BOLOGNA, DEPT OBSTET & GYNECOL 2, I-40123 BOLOGNA, ITALY