[1] McMaster Univ, Dept Obstet & Gynecol, Hamilton, ON, Canada
[2] McMaster Univ, Dept Radiol, Hamilton, ON, Canada
[3] Canadian Premature Babies Fdn, Etobicoke, ON, Canada
[4] McMaster Univ, Fac Social Sci, Dept Hlth Aging & Soc, Hamilton, ON, Canada
[5] McMaster Univ, Dept Hlth Res Methods Evidence & Impact, Div Maternal Fetal Med, Hamilton, ON, Canada
[6] McMaster Univ, Dept Obstet & Gynecol, 1280 Main St W, Hamilton, ON L8S 4L8, Canada