[1] Hosp Sick Children, Div Cardiol, Dept Pediat, Fetal Cardiac Program, Toronto, ON M5G 1X8, Canada
[2] Mt Sinai Hosp, Div Maternal Fetal Med, Toronto, ON M5G 1X5, Canada
[3] Womens Coll Hosp, Toronto, ON M5S 1B2, Canada
[4] Univ Toronto, Toronto, ON, Canada