• headache;
  • migraine;
  • pregnancy;
  • parity;
  • trimester;
  • epidemiology

Background.— In previous studies, pregnancy has been associated with less headache, but the influence of parity on this association is largely unknown.

Objectives.— To examine the prevalence of headache and migraine among pregnant women, and explore the relation of headache to parity in a large, population-based study.

Methods.— In the Nord-Trøndelag Health Study in Norway 1995-1997 (HUNT 2), a total of 27,700 (60%) out of 46,506 invited women responded to headache questions (Head-HUNT). In total, 9281 women were 40 years or younger and responded to questions on pregnancy and birth, and 550 of these reported to be pregnant when filling in the questionnaire. A total of 20,287 women who were 70 years or younger and reported not to be pregnant responded to questions on headache and reported number of child births.

Results.— Adjusting for age and educational level, the headache prevalence was lower among pregnant than among nonpregnant women. The association between headache and pregnancy was significant for nulliparous (one who has never given birth) (OR = 0.5, 95% CI = 0.4-0.7), but not for primiparous (1 child only) and multiparous (several children) women (OR = 0.8, 95% CI = 0.7-1.0). This was evident for both migraine and nonmigrainous headache. Among nonpregnant women, there was an increased headache prevalence among primi- and multiparous women compared with nulliparous (OR = 1.3, 95% CI = 1.2-1.4).

Conclusion.— Headache, both migraine and nonmigrainous, was less prevalent in nulliparous pregnant women compared with all nonpregnant women, and to nulliparous nonpregnant women. Headache was less prevalent in the third trimester of pregnancy, but not in the first and second trimesters, compared with nonpregnant women. Also in nonpregnant women, headache was less prevalent in nulliparous than in primi- and multiparous women.