Parity and decreased use of oral contraceptives as predictors of asthma in young women

Clin Exp Allergy. 2006 May;36(5):609-13. doi: 10.1111/j.1365-2222.2006.02475.x.


Background: Asthma is more prevalent among males in childhood, but females report higher rates in adulthood. The reasons are unknown; although it has been hypothesized that hormonal factors may explain this sex-dependent risk of adult-onset asthma.

Objective: To determine whether a woman's reproductive history or use of oral contraceptives is associated with adult-onset asthma.

Methods: In 1991-1993, we surveyed 681 women aged 29-32 years randomly sampled from participants first surveyed at age 7 years by the 1968 Tasmanian Asthma Survey, a study of all children born in 1961 and attending school. Current asthma was defined as reporting asthma or wheezy breathing in the past 12 months.

Results: In women who did not have asthma or wheezy breathing by age 7 years, 13% had current asthma. The risk of current asthma in these who were parous increased with the number of births (odds ratio (OR) 1.50 per birth, 95% confidence interval (CI) 1.01-2.23 P=0.04) while women with one birth were at a lower risk than nulliparous women (OR 0.46 95% CI 0.2-1.06, P=0.07). Independent of parity, the risk decreased by 7% (95% CI 0-13%) per year of oral contraceptive pill use in all women. In women who did have asthma or wheezy breathing by age 7 years, neither reproductive history nor oral contraceptive pill use predicted current asthma.

Conclusion: Our observation that parity and decreased oral contraceptive use predict asthma in women, is consistent with the hypothesis that the asthma that develops after childhood is in part a response to endogenous and exogenous female hormones. This may be due to alterations of cytokine responses by the pregnant state, triggering adult-onset asthma in women.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Age Factors
  • Asthma / epidemiology
  • Asthma / etiology*
  • Contraceptives, Oral / administration & dosage*
  • Educational Status
  • Female
  • Follow-Up Studies
  • Humans
  • Parity*
  • Pregnancy
  • Prevalence
  • Prospective Studies
  • Respiratory Sounds
  • Risk Factors
  • Smoking / adverse effects
  • Tasmania / epidemiology


  • Contraceptives, Oral