[1] Massachusetts Gen Hosp, Dept Obstet & Gynecol, Boston, MA 02114 USA
[2] Massachusetts Gen Hosp, Div Obstetr Anesthesia, Boston, MA 02114 USA
[3] Massachusetts Gen Hosp, Div Cardiac Anesthesia, Boston, MA 02114 USA
[4] Massachusetts Gen Hosp, Dept Anesthesia Crit Care & Pain Med, Boston, MA 02114 USA
[5] Massachusetts Gen Hosp, Dept Surg, Boston, MA 02114 USA
[6] Harvard Univ, Sch Med, Dept Obstet Gynecol & Reprod Biol, Boston, MA 02115 USA
[7] Harvard Univ, Sch Med, Dept Anesthesia, Boston, MA 02115 USA
[8] Harvard Univ, Sch Med, Dept Surg, Boston, MA 02115 USA