Maternal smoking during pregnancy and primary headache in school-aged children: a cohort study

Background: It is not known whether smoking by mothers during pregnancy is associated with headache in their offspring. Methods: Two prospective cohorts of 869 children aged 10-11 years from Ribeirao Preto (RP) and 805 children aged 7-9 years from Sao Luis (SL) were studied. Data on maternal smoking were collected at birth. Primary headache was defined as a reporting of >= 2 episodes of headache in the past 2 weeks, without any associated organic symptoms. Results: Prevalence of headache was 28.1% in RP and 13.1% in SL as reported by the mothers and 17.5% in RP and 29.4% in SL as reported by the children. Agreement between mothers' report and children's self-report of primary headache in the child was poor. After adjustment, children whose mothers smoked >= 10 cigarettes per day during pregnancy presented higher prevalence of primary headache than their counterparts in both cohorts, as reported by the mother and in RP as reported by the children. Conclusions: Maternal smoking during pregnancy was associated with headache in 7- to 11-year-olds. With one exception, the consistency of the results, despite poor agreement between maternal and children reports of headache, indicates that maternal smoking during pregnancy may contribute to headaches in their children.