Anti-CGRP antibodies in early pregnancy were linked to more spontaneous abortion

Design

Retrospective cohort study using the AM-PREGNANT cohort from a US commercial claims database, Cox models

Population

7,579 singleton pregnancies in 7,119 people with pre-existing migraine

Primary outcome

Spontaneous abortion at 20 weeks or earlier

Effect

Anti-CGRP antibodies aHR 1.42 (95% CI 1.12 to 1.80); propranolol aHR 1.02 (0.71 to 1.47)

A claims-based cohort followed 7,579 pregnancies in 7,119 people with pre-existing migraine, drawn from a US commercial database for 2018 to 2021. Exposure was any filled prescription or injection claim for an anti-CGRP monoclonal antibody (erenumab, fremanezumab, galcanezumab or eptinezumab) or propranolol during follow-up to 20 weeks.

There were 1,862 spontaneous abortions overall. Anti-CGRP antibody exposure was associated with a higher hazard of spontaneous abortion than no exposure (adjusted HR 1.42, 95% CI 1.12 to 1.80), similar in bias-adjusted analysis (HR 1.33). Propranolol exposure was not associated with increased risk (adjusted HR 1.02, 95% CI 0.71 to 1.47).

The antibody-exposed group was small and may differ in migraine severity and other risks. Claims data cannot confirm the timing of conception or what was taken. The authors call for further evaluation, which is the right reading.

• Discuss contraception and pregnancy plans before starting an anti-CGRP antibody in people who could become pregnant
• When a patient becomes pregnant on one, review the need for it with her and her obstetric team rather than stopping on a single study
• Propranolol showed no signal here, but it has its own pregnancy considerations
• Report exposures to registries or pharmacovigilance where available

Why it matters

These agents have limited pregnancy data, and CGRP has a role in placental development, so an early signal merits attention.

Don't overread it

This is an association from claims data; it does not show that the antibodies cause miscarriage.

The statistics, in plain English

An adjusted hazard ratio of 1.42 means a 42% higher rate of spontaneous abortion at any point in follow-up among exposed people, compared with unexposed. The interval (1.12 to 1.80) excludes no effect, but a single observational study with a small exposed group is far from proof. Women with more severe migraine, who are more likely to receive these drugs, could have a different baseline risk.

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