[1] HLTH & WELF CANADA,LAB CTR DIS CONTROL,DIV BIOMETR,OTTAWA K1A 0L2,ONTARIO,CANADA
[2] HLTH & WELF CANADA,LAB CTR DIS CONTROL,BUR CMMINICABLE DIS EPIDEMIOL,OTTAWA K1A 0L2,ONTARIO,CANADA
[3] UNIV WESTERN ONTARIO,DEPT PSYCHOL,LONDON N6A 3K7,ONTARIO,CANADA
[4] UNIV WESTERN ONTARIO,DEPT OBSTET & GYNECOL,LONDON N6A 3K7,ONTARIO,CANADA
[5] QUEENS UNIV,SOCIAL PROGRAM EVALUAT GRP,KINGSTON K7L 3N6,ONTARIO,CANADA
[6] UNIV BRITISH COLUMBIA,VANCOUVER GEN HOSP,DEPT MED,VANCOUVER V5Z 1M9,BC,CANADA