[1] Fac Med & Hlth, Sch Populat Hlth, UNSW Sydney, Sydney, NSW 2052, Australia
[2] Univ Iceland, Fac Med, Ctr Publ Hlth Sci, Reykjavik, Iceland
[3] Fac Med & Hlth, Natl Drug & Alcohol Res Ctr, UNSW Sydney, Sydney, NSW, Australia
[4] Royal Hosp Women, Dept Maternal Fetal Med, Sydney, Australia
[5] Childrens Hosp Westmead, Clin Sch, Childrens Hosp, Sydney, NSW, Australia