Sandström, A
Altman, M
Cnattingius, S
Johansson, S
Ahlberg, M
Stephansson, O
Article History
Received: 22 July 2016
Revised: 5 October 2016
Accepted: 14 October 2016
First Online: 8 December 2016
Competing interests
: The authors declare no conflict of interest.