If your twins are a boy and a girl then you do not need to complete this questionnaire.
Please write your Family ID Number in the box:
It would be really helpful for us to be able to contact you by email. If you are happy to provide this information please enter it below.
To begin the questionnaire, click the 'next' button.
For further information about the study, please contact Dr Ellen van Jaarsveld, Health Behaviour Research Centre, Dept of Epidemiology & Public Health, UCL, 1-19 Torrington Place, London WC1E 7HB Email: