Migraine is a very common neurological condition, and it occurs at even greater rates in women.
Migraine attacks are notoriously difficult to treat: regular painkillers like NSAIDs and acetaminophen often just don't cut it.
In 2018, a new class of injected medications was approved for migraine treatment, as an option for patients who do not respond to mainstream oral treatments like triptans or ergotamine.
But new research published in JAMA Neurology suggests this treatment may also raise the risk of miscarriage among expectant parents.
The medications are called CGRP-targeted monoclonal antibodies (mAbs), and they work by blocking CGRPs (calcitonin gene-related peptides). They tend to have fewer side effects than other migraine medicines, and fewer drug interactions.
CGRPs are "inherently involved" in migraine attacks, but they also play a role in regulating blood flow, embryo implantation, and placental development during pregnancy.
The new study, led by epidemiologist Anick Bérard of Centre Hospitalier Universitaire Sainte-Justine in Canada, suggests CGRP-blocking mAbs may interfere with a developing pregnancy, although the evidence is still quite limited at this stage.
The study is observational, which means it can only identify associations, not establish a cause.
Drawing from an existing patient dataset collected by private health insurers between 2018 to 2021, the researchers analyzed the first 20 weeks of 7579 pregnancies from mothers who, according to their health records, either had an official migraine diagnosis or had been prescribed triptan or ergot medications within the six months preceding their last menstrual period.
Some of these mothers were also prescribed anti-CGRP mAbs (erenumab, fremanezumab, galcanezumab, or eptinezumab) or propranolol during or in the six months prior to their pregnancy. The researchers analyzed the data by estimated days of exposure to these two medications (hence 'person-time').
"Anti-CGRP monoclonal antibody exposure was associated with an increased risk of spontaneous abortion compared with unexposed person-time, while propranolol exposure was not," Bérard and team report.
Within the first 20 weeks of pregnancy, there was about 40 percent higher chance of miscarriage among mothers exposed to anti-CGRP mAb therapy, compared to no exposure, while propranolol was not associated with any increased risk.
While these results are concerning, if you are a migraine patient who wants to get pregnant, you should discuss your treatment and the risks with your doctor before making any changes to your medication regime.
A study like this cannot show that a particular medication necessarily causes miscarriage.
Since these drugs are typically prescribed for treatment-resistant and severe migraines, it's possible that the migraines themselves may be involved in raising miscarriage risk.
There are several other limitations with the data.
The records are based on a commercially insured US population, meaning the results may not apply to uninsured or publicly insured individuals, or people in other countries.
Insurance records are also not necessarily collected with rigorous health research in mind: for example, the records used in this study don't account for how severe each individual's migraines were, whether the prescribed medications were actually taken, or whether pregnancies were planned.
The authors say this study underscores the need for further research into the safety of anti-CGRP mAbs during pregnancy.
"Given the increasing use of anti-CGRP mAbs for migraine prevention among individuals of reproductive age, further research is needed to evaluate their safety during pregnancy, including studies examining spontaneous abortion, fetal outcomes, and longer-term offspring outcomes," the authors write.
"Until more evidence is available, clinicians should consider the limited evidence on pregnancy safety when discussing anti-CGRP mAb treatment with individuals who may become pregnant."
The research has been published in JAMA Neurology.
This article was fact-checked by Fiona MacDonald and edited by Fiona MacDonald. While we pride ourselves on our process, we are only human. If you spot a mistake, please let us know.