[1] Univ Colorado, Ctr Hlth Sci, Perinatal Res Ctr, Dept Pediat,Div Perinatal Med, Aurora, CO 80045 USA
[2] Univ Milan, Dept Obstet & Gynecol, Milan, Italy
[3] Washington Univ, Sch Med, Dept Pediat, St Louis, MO 63110 USA
[4] Univ Manchester, St Marys Hosp, Dept Child Hlth, Manchester M13 0JH, Lancs, England
[5] Univ Florida, Coll Med, Dept Pediat, Gainesville, FL USA
[6] Univ Gothenburg, Perinatal Ctr, Dept Physiol & Pharmacol, Gothenburg, Sweden