Although the AOB cohort demonstrated a retention rate of 90% of participants between the first and third questionnaire, there was an 86% response rate for the 12 month data collection.
Second and third questionnaires for non responders were mailed.
Therefore, different nurses and physicians might have filled in the first, second and third questionnaires and changes in expectations might be influenced by the different respondents.
The second and third questionnaires will be sent by regular mail to participants, accompanied by reply-paid envelopes.
In the second and third questionnaires, mothers were asked whether they smoked in the previous 2 months (no, yes).
The second and third questionnaires were also pre-treatment baseline questionnaires, completed at the first two visits (pre-baseline screening W−2 and baseline W0).
In the second and third questionnaires (at the end of these study periods) it was also asked whether the nurse or physician had filled in a previous questionnaire.
The second and third questionnaires were distributed by mail, together with a prepaid return envelope and a covering letter stating the purpose of the study and guaranteeing confidentiality.
In the second and third questionnaires, the mothers were asked whether they had smoked during the past 2 months (yes/no).
Of all women who started their pregnancy in midwife-led care, 2398 individuals filled in both the second and third questionnaires.
