Of approximately 1300 eligible men, 1064 agreed to participate in the trial. Of these, we included 777 men who were first-time fathers,had completed the follow-up questionnaire and whose partner had planned a vaginal childbirth,
elective caesarean deliveries excluded.This sample was divided into three groups on the basis of paternal age in mid-pregnancy. There is no consensus regarding the definition of ‘advanced’ paternal age and different age cut-offs have been used,for instance in studies of male fertility: 30 years