Thank you for your question.
For the benefit of our readers, Botulinum toxin is an injectable drug that reduces fine lines and wrinkles by inhibiting the communication between your nerve cells and muscle. This paralyzes or weakens the muscle to prevent it from causing wrinkling in your skin.
Very little research has been done on Botox’s safety during pregnancy, and the same would go for Botox while breastfeeding. So in this way, it's probably not a good idea. I don't think your having the one treatment will do any harm, but you can mention it to your physician at your next check-up.