Migraine diagnosed before pregnancy is associated with adverse outcomes during pregnancy

Women are disproportionately affected by migraines, especially during their childbearing years. However, the relationship between migraine and adverse pregnancy outcomes has not been well understood. A new study conducted by investigators from Brigham and Women’s Hospital, a founding member of General Brigham and General Healthcare System, analyzed data from thousands of women from the Nurses’ Health Study II to assess the relationship between migraines and pregnancy complications. In a paper published in Neurologythe team reported that migraine diagnosed before pregnancy was associated with adverse outcomes during pregnancy, including premature delivery, gestational hypertension, and pre-eclampsia, suggesting that migraine may be a clinical sign of higher obstetric risk.

Premature birth and hypertensive disorders are some of the primary drivers of maternal and infant morbidity and mortality. Our findings suggest that a history of migraine warrants consideration as an important risk factor for this complication and could be useful in reporting women who might benefit from enhanced monitoring during pregnancy.”

Alexandra Purdue-Smith, PhD, senior author, senior epidemiologist at Brigham and Women’s Hospital and instructor in medicine at Harvard Medical School.

Women are two to three times more likely than men in their lifetime to experience a migraine, and migraines are most prevalent among women between the ages of 18 and 44. For some, migraine can be accompanied by an aura (5.5% of the population), which is usually a visual disturbance that appears before the onset of the headache.

Adverse pregnancy outcomes and migraine, especially migraine with aura, are consistently associated with higher risks of coronary heart disease and stroke in women according to previous studies. The underlying biology responsible for these risks may also increase the likelihood of pregnancy complications. But so far, only a handful of small or retrospective studies have examined migraine as a risk factor for pregnancy complications. No prospective studies have examined the risks of the aura phenotype (migraine with and without aura).

Purdue-Smith and colleagues analyzed data from the Nurses’ Health Prospective Study II, which included 30,555 pregnancies from 19,694 US nurses. The investigators looked at the migraine and migraine phenotype (migraine with and without aura) self-reported before pregnancy and the incidence of self-reported pregnancy outcomes.

Because of the large size of the study population and the availability of data on other health and behavioral factors, the researchers could control for potential confounding factors in their analyses, such as body mass index, chronic hypertension, and smoking.

The researchers found that migraine before pregnancy was associated with a 17 percent higher risk of preterm labor, a 28 percent higher rate of gestational hypertension, and a 40 percent higher rate of preeclampsia than without migraine. Migraine with aura was associated with a slightly increased risk of pre-eclampsia compared with migraine without aura. Migraine was not associated with low birth weight or gestational diabetes.

Participants with migraines who reported using aspirin regularly (more than twice a week) before pregnancy were 45 percent less likely to have a premature birth. The U.S. Preventive Services Task Force currently recommends low-dose aspirin during pregnancy for individuals at risk of pre-eclampsia and those with more than an average risk factor for pre-eclampsia. Clinical trials have shown that low-dose aspirin during pregnancy is also effective in reducing preterm labor rates. However, Purdue-Smithe notes that migraine is not currently included among the indications for aspirin use in pregnancy. Our findings of a reduced risk of preterm labor among women with migraine who reported regular aspirin use before pregnancy suggest that aspirin may also be beneficial for women with migraine. Given the observational nature of our study, the lack of detailed information on aspirin dosage is available. On set, clinical trials will be needed to definitively answer this question.”

Some other limitations of the study include, that participants were only reported if they had a medical diagnosis of migraine, and those who did not suffer from chronic or severe migraines were likely excluded. Moreover, the aura was evaluated after the diagnosis of migraine and after several pregnancies in the group, which may lead to some degree of reverse causation in analyzes examining the migraine phenotype. In addition, the cohort study consisted of predominantly white, non-Hispanic individuals with relatively high socioeconomic status and health literacy, which may limit generalizability.