- Researchers at Brigham and Women’s Hospital in Boston conducted a large prospective study to better understand the association between migraines and adverse pregnancy outcomes.
- They reported that women with pre-pregnancy migraines had a 17% higher risk of preterm delivery, a 28% higher risk of gestational hypertension, and a 40% higher risk of preeclampsia compared to those without pre-pregnancy migraines.
- They say that these findings suggest that pregnant women with a history of migraine may benefit from closer monitoring during pregnancy.
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Some individuals experience an “aura” before a migraine headache, which frequently involves flashing lights in the field of vision.
A recent meta-analysis showed that migraine, particularly with an aura, is associated with two-fold higher risk of stroke and myocardial infarction.
Researchers have hypothesized that the biological characteristics responsible for cardiovascular risks in people with migraine might also increase the risk of pregnancy complications.
However, to date, few studies have examined the link between migraine and pregnancy complications. These studies are limited by small study populations and a lack of information on potential confounding factors and the migraine phenotype (with or without aura).
With these gaps in mind, researchers at Brigham and Women’s Hospital in Boston designed a large, prospective study to estimate the associations of pre-pregnancy migraine with risk of gestational diabetes, gestational hypertension, pre-eclampsia, pre-term delivery, and low birthweight.
In the study, published in the journal Neurology, the researchers also sought to determine whether these associations vary by migraine phenotype and to examine potential effect modification by aspirin use.
Details from the pregnancy and migraine study
To accomplish these objectives, Alexandra Cari Purdue-Smithe, Ph.D., an instructor in medicine at Brigham, and her colleagues used data from the Nurses’ Health Study II (NHSII).
This study was established in 1989 and enrolled 116,430 registered nurses in the United States aged 25 to 42 years. Participants were asked to complete questionnaires on their health and lifestyle. For the purpose of this study, participants were asked to complete questionnaires on their health and lifestyle every two years.
In 2007, NHSII participants were asked if they ever experienced aura with their migraine headaches and, in 2009, participants recorded details about each pregnancy in their lifetime, including adverse pregnancy outcomes.
For this study, Purdue-Smithe’s team defined migraine as any self-reported physician diagnosis of migraine on the 1989, 1993 and 1995 NHSII questionnaires.
They limited their analyses to pregnancies lasting at least 20 weeks in women without a history of cardiovascular disease, type 2 diabetes, and cancer (30,555 pregnancies in 19,694 women).
The researchers calculated the relative risk and 95% confidence interval for each adverse pregnancy outcome using log binomial and log Poisson models, which were adjusted for various confounding factors (age at pregnancy, age at onset of menstruation, race/ethnicity, body mass index, chronic hypertension, alcohol consumption, physical activity, smoking status, analgesic use, oral contraceptive use, infertility diagnosis, and number of births.)
Key findings of the migraine study
Out of 19,694 women, 11% had a history of physician-diagnosed migraine at baseline.
The results of the statistical analyses showed that migraine was not associated with gestational diabetes or low birth weight, but it was associated with a 17% higher risk of preterm delivery, a 28% higher risk of gestational hypertension, and a 40% higher risk of preeclampsia.
The risk of preterm delivery and risk of gestational hypertension were similar for migraine with and without aura. However, the risk of preeclampsia was somewhat higher among women who experienced migraine with aura than those who had migraine without aura.
The researchers also reported that women with migraine who took aspirin regularly (more than twice a week) before their pregnancy had a 45% lower risk of preterm delivery. The researchers also observed a qualitatively lower risk of preeclampsia for women who reported regular aspirin use before pregnancy, but this particular analysis had low statistical power.
Understanding migraine and pregnancy
Dr. Matthew Robbins, an associate professor of neurology at Weill Cornell Medicine in New York who was not involved in the study, said the findings are important.
“We have already known from large, population-based, epidemiological studies that the relative risk of stroke and overall cardiovascular comorbidity is higher in individuals who have migraine with aura,” he told Medical News Today. “Now, we know that this risk may extend to complications of pregnancy including a higher rate of pregnancy-specific cardiovascular conditions such as gestational hypertension and preeclampsia.”
“The findings of this study suggest that migraine history and, to a lesser extent, migraine phenotype, are clinically useful markers of pregnancy risks,” he added.
Dr. Sarah E. Vollbracht, an associate professor of neurology at Columbia University in New York who also was not involved in the study,
“Given the high prevalence of migraine in women of childbearing age, these findings suggest that migraine screening should be included in initial obstetrical assessments to determine if a woman is at risk of adverse pregnancy outcomes and women with migraine should be closely followed throughout pregnancy and monitored for the development of hypertensive disorders in pregnancy,” she told Medical News Today.
The results of this study also suggest that regular pre-pregnancy aspirin use in women with migraine may decrease the risk of preterm delivery and preeclampsia, but Vollbracht noted that “this finding should be interpreted cautiously” as “more data, including placebo-controlled studies, is needed to determine the role of aspirin use in pregnant women with migraine”.
Limitations and future research
Purdue-Smithe and her co-authors noted that the definition of migraine used in this study may have underestimated the true prevalence of migraine in the study population and, accordingly, the relative risks.
Although the statistical analyses took many potential confounding factors into account, confounding effects from other factors, such as genetics and migraine-specific medications, cannot be excluded.
The Nurses’ Health Study II cohort is comprised of mostly non-Hispanic white study participants, which limits generalizability.
“Future studies should aim to include a more diverse patient population from different racial, ethnic, and socioeconomic backgrounds,” Vollbracht said.
She added that “further prospective studies are needed to determine more clearly the difference in risk based on migraine phenotype as well as understanding the influence of attack frequency on risk of these adverse pregnancy outcomes.”
Additional research on effect modification by aspirin is needed, particularly with regards to optimal timing of initiation and dosage.
“Future studies may need to assess the use of preventive measures against preeclampsia for pregnant women with migraine with aura, such as daily aspirin during the second and third trimesters,” said Robbins.
Finally, the researchers noted that future research should also seek to clarify the mechanisms underlying the associations revealed in this study.
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