Analysis of 29 years of postmarketing data provides further reassurance on exposures in early pregnancy.

To examine the long-term safety of onabotulinumtoxinA use preconception and following pregnancy, researchers conducted a manufacturer-sponsored study including patients treated with onabotulinumtoxinA during pregnancy or three months or less prior to conception during a 29-year period. Participants were identified via postmarketing surveillance using the Allergan Global Safety Database. Data for birth defects of any live births during this time period were included.

Among 913 pregnancies identified, 397 (44%) had known outcomes. The most common indications for onabotulinumtoxinA in this cohort were aesthetic  (35%) and migraine or headache (30%).  In 318 of these pregnancies, 94.6% of onabotulinumtoxinA exposure occurred within three months before conception or during the first trimester. Among 242 women with known onabotulinumtoxinA dose, 84% were exposed to less than 200U of the drug. Among the 152 live births in the cohort, there was one major birth defect, two minor fetal defects and one birth complication. The overall fetal defect prevalence rate was 2.6% (4/152; 95% confidence interval [CI], 1.0% to 6.6%). The major fetal defect prevalence rate was 0.7% (1/152; 95% CI, 0.1% to 3.6%), which was comparable to rates reported in the general population (3% to 6%).

Comment: The use of various subtypes and brands of botulinum toxins has increased worldwide, especially with younger women using these drugs for aesthetics and headaches. In a previous analysis, onabotulinumtoxinA-exposed mothers had a prevalence of major fetal defects (0.9%; 1/110) comparable to background rates in the general population, and the current study has confirmed this finding. Although postmarketing database reviews are subject to missing data, the almost 30-year follow up was reassuring. The information from this study will be useful for shared decision making. Most notable for clinicians to pay attention to when counselling patients was the lack of data for second- and third-trimester exposures.

Note to readers: At the time we reviewed this paper, its publisher noted that it was not in final form and that subsequent changes might be made.

Michael S. Okun, MD, Adelaide Lackner Professor and Chair of Neurology and Executive Director, Fixel Institute for Neurological Diseases, University of Florida McKnight Brain Institute, Gainesville, USA.

Brin MF, et al. Pregnancy outcomes in patients exposed to onabotulinumtoxinA  treatment: a cumulative 29-year safety update. Neurology 2023 May 3;  e-pub (https://doi.org/10.1212/WNL. 0000000000207375).

This summary is taken from the following Journal Watch title: Neurology.