ScienceNot yet confirmed elsewhere1 publisher2 min readPublished
Pregnancies exposed to CGRP migraine antibodies carried about 40% higher miscarriage risk in US insurance data
Anick Bérard's team reports about 40% higher miscarriage risk with CGRP-blocking migraine antibodies in a JAMA Neurology study of insurance records. The design is observational, so it can inform counseling but cannot show that the drugs cause miscarriage.
The Scientist · Science desk
Mothers exposed to anti-CGRP antibodies had about a 40 percent higher chance of miscarriage within the first 20 weeks than with no exposure. The study analyzed 7,579 pregnancies from private health insurer data, 2018 to 2021. CGRP-targeted antibodies were approved in 2018.
| Figure | Value | Note | Claim |
|---|---|---|---|
| Pregnancies analyzed, private insurer data 2018-2021 | 7,579 pregnancies | 4 | |
| First weeks of pregnancy | 20 weeks | 2 | |
| CGRP antibodies approved | 2,018 year | 8 |
What happened
- The researchers drew on private health insurer data from 2018 to 2021, covering the first 20 weeks of 7,579 pregnancies in mothers with a migraine diagnosis or a triptan or ergot prescription.
- Exposure was defined as a prescription for erenumab, fremanezumab, galcanezumab, eptinezumab or propranolol, during pregnancy or in the six months before it.
- CGRP drives migraine attacks and also helps regulate blood flow, embryo implantation and placental development, which is the biological reason the class is a candidate for pregnancy effects.
- The antibodies were approved in 2018 as an injected option for patients who do not respond to oral treatments such as triptans or ergotamine.
Why it matters
- decision A patient on one of these antibodies who is pregnant or may become so has a specific question for the prescriber, and ScienceAlert advises raising it before any change to medication.
- constraint The estimate comes from commercially insured US patients, so it may not hold for uninsured or publicly insured patients or for patients in other countries.
- precedent Firmer guidance depends on studies of spontaneous abortion, fetal outcomes and longer-term offspring outcomes, which the authors say are still needed.
The paper's most useful design choice is its second drug. Propranolol was analysed alongside the four antibodies, and it showed no added miscarriage risk [3]. "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 wrote [12]. Every pregnancy in the cohort met a migraine criterion, either a diagnosis or a triptan or ergot prescription [4], so the propranolol result argues against a blanket effect of having migraine.
It leaves open an effect of severe migraine. The antibodies are typically prescribed for treatment-resistant and severe disease, and ScienceAlert notes that the migraines themselves may be involved in raising miscarriage risk [9]. The insurance records do not account for migraine severity, for whether prescribed drugs were actually taken, or for whether pregnancies were planned [11]. The thing this doesn't tell you is whether the propranolol group was as ill as the antibody group.
On the denominator: the 7,579 is the whole cohort [4]. ScienceAlert's account of the paper does not say how many of those pregnancies involved an antibody, what the absolute miscarriage rates were, or how wide the interval is around the 40% [17]. The analysis counted estimated days of exposure [6], so the figure compares exposed person-time with unexposed person-time [2]. A 40% relative rise on a low baseline is a small absolute change. On a high baseline it is a larger one.
The authors' own advice is modest. "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," they wrote [13]. We think that is the right weight. The study is observational and can identify only associations [16], and the severity question is still open.
What to watch
- A replication in publicly insured or non-US patients, which would test whether the 40% holds outside commercially insured US records.
- Publication of exposed-pregnancy counts, absolute miscarriage rates and an interval around the 40%, so the relative figure can be read against a baseline.
- Analyses that capture migraine severity and whether prescribed antibodies were taken, the two gaps that leave the drug and the disease entangled.
Clarity's read
What the record supports and how the coverage leans. The claims behind it follow.
Reality
- Evidence40
- Adoption
- Insufficient
- Hype gap+10
- Incentives
- Insufficient
- Confidence45
Claim ledger
Ranked by verification strength, evidence, and original report placement.
- [1]
The study was published in JAMA Neurology and led by epidemiologist Anick Bérard of Centre Hospitalier Universitaire Sainte-Justine in Canada.
- [2]
Within the first 20 weeks of pregnancy, there was about a 40 percent higher chance of miscarriage among mothers exposed to anti-CGRP mAb therapy, compared with no exposure.
- [3]
Propranolol exposure was not associated with any increased risk of miscarriage.
- [4]
The researchers used private health insurer data from 2018 to 2021 and analyzed the first 20 weeks of 7579 pregnancies from mothers who had an official migraine diagnosis or a triptan or ergot prescription in the six months before their last menstrual period.
- [5]
Some of these mothers were also prescribed anti-CGRP mAbs (erenumab, fremanezumab, galcanezumab or eptinezumab) or propranolol during or in the six months before their pregnancy.
- [6]
The researchers analyzed the data by estimated days of exposure to the two medications, known as person-time.
- [7]
CGRPs are inherently involved in migraine attacks, but they also play a role in regulating blood flow, embryo implantation and placental development during pregnancy.
- [8]
CGRP-targeted monoclonal antibodies were approved in 2018 as an injected option for patients who do not respond to mainstream oral treatments such as triptans or ergotamine.
- [9]
These drugs are typically prescribed for treatment-resistant and severe migraines, so it is possible that the migraines themselves are involved in raising miscarriage risk.
- [10]
The records are based on a commercially insured US population, so the results may not apply to uninsured or publicly insured individuals, or to people in other countries.
- [11]
The insurance records do not account for how severe each person's migraines were, whether the prescribed medications were actually taken, or whether pregnancies were planned.
- [12]
"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.
- [13]
"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."
- [14]
The authors say further research is needed on the safety of anti-CGRP mAbs during pregnancy, including studies of spontaneous abortion, fetal outcomes and longer-term offspring outcomes.
- [15]
ScienceAlert advises migraine patients who want to get pregnant to discuss their treatment and the risks with their doctor before making any changes to their medication.
- [16]
The study is observational, which means it can only identify associations, not establish a cause.
- [17]
ScienceAlert's account reports the cohort size (7579 pregnancies) and an approximate 40% higher miscarriage risk, but does not report the number of antibody-exposed pregnancies, absolute miscarriage rates, or a confidence interval.
Sources
1 independent publisher whose own reporting we read for this story.
- sciencealert.comA Newer Class of Migraine Drugs Is Linked to a 40% Rise in Miscarriage Risk
1 article · October 12, 2026
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