[1] Univ Maryland, Sch Med, Dept Obstet Gynecol & Reprod Sci, Baltimore, MD 21201 USA
[2] Univ Autonoma Barcelona, Dept Obstet, Fetal Med Unit, Vall dHebron Hosp, E-08193 Barcelona, Spain
[3] Inst Salud Carlos III, Maternal & Child Hlth & Dev Network SAMID RD 08 0, Barcelona, Spain
[4] Univ Auckland, Liggins Inst, Auckland 1, New Zealand
[5] Univ Auckland, Dept Obstet & Gynaecol, Auckland 1, New Zealand