Migraine headaches are among the leading causes of disability in the world. The burden of migraines is highest in women of reproductive age. This cross-sectional study characterized the prevalence, symptoms and correlates of migrainous headaches in 154 pregnant women attending a prenatal care clinic in Lima, Peru. Lifetime prevalence of migraine defined by modified IHS criteria was 9.1% (95% CI 4.6-13.6). When probable migraines were included, the lifetime prevalence of migraine in this population was 29.2% (95% CI 22.0-36.4). Migraine headaches were associated with a maternal history of headache, childhood carsickness, a diagnosis of allergies, and a high frequency of fatigue. Although headache-related disability was low in terms of missed work and recreation, high rates of headache pain and medicinal use reflect the true impact on this population.