Although migraine is one of the commonest chronic disorders in women and frequently affects those of reproductive age, its effects on pregnancy have not been studied in detail. The investigators utilized data collected as part of a population-based study of congenital anomalies to evaluate the relationship between a history of maternal migraines and pregnancy outcomes. They reviewed the pregnancy histories of 38,151 structurally normal newborn infants who were born in the years 1980-1996. The mothers of 713 infants, 1.9% of the total, had severe migraine with and without aura during pregnancy. In all cases, migraine had begun before the study pregnancy and one or more episodes occurred during pregnancy-chiefly in the third month of gestation. Pregnant women with severe migraine had a significantly higher prevalence of preeclampsia (odds ratio, 1.4; 95% confidence intervals, 1.1-1.8) and severe nausea and vomiting (OR, 1.5; CI, 1.2-1.8), while rates of threatened abortion (OR, 0.7; CI, 0.6-0.9) and preterm delivery (OR, 0.8; CI, 0.6-0.9) were significantly lower than in migraine-free women. The rates of placental disorders, prolonged pregnancy, gestational diabetes, poly- and oligohydramnios, and anemia were the same in both groups. Pregnant women with and without migraine had a similar incidence of acute medical disorders such as respiratory infections and digestive system or genital tract problems. The incidence of urinary tract infections was lower in women with migraine. The rates of chronic diseases like diabetes and epilepsy were similar in women with and without migraine, while women with migraine were more likely to have cardiac dysrhythmias (OR, 8.8; CI, 5.0-13.6), thyroid disease (OR, 3.0; CI, 1.4-6.4), and panic disorder (OR, 4.7; CI, 2.8-7.8) than those without headaches. In terms of pregnancy outcome, the proportion of male infants, the mean gestational age, the mean birth weight, and the numbers of post term births were comparable in newborn infants whose mothers had or did not have migraine. No difference in these variables was found between male and female infants born to mothers with or without migraine.