[1] Queens Univ Belfast, Sch Nursing & Midwifery, 97 Lisburn Rd, Belfast BT9 7BL, Antrim, North Ireland
[2] Lakehead Univ, Sch Nursing, 955 Oliver Rd, Thunder Bay, ON P7B 5E1, Canada
[3] Univ Toronto, Lawrence S Bloomberg Fac Nursing, 155 Coll St, Toronto, ON M5T 1P8, Canada
[4] SUNY Stony Brook, Dept Psychol, Stony Brook, NY 11794 USA
[5] Univ Oxford, Nuffield Dept Populat Hlth, Natl Perinatal Epidemiol Unit, Oxford OX3 7LF, England