There have not been any studies showing that Botox is responsible for birth defects. The Australian article is about a single unfortunate case of a child being born deaf and blind. Its mother had received Dysport injections (a form of Botox) during her first month of pregnancy.
With the millions of women who have received Botox injections, it stands to reason that many have received treatment in the first week or two of their pregnancy before they were aware that they were pregnant. That having been said, this is exactly the reason why it is not recommended to have Botox injections when pregnant.
Birth defects unfortunately occur all too often, and even if coincidental and unrelated to Botox injections, the injections may be cited as the cause, and put the injecting physician in "hot water". It is best to avoid any elective medical procedures during pregnancy.
Enjoy the "Glow of Pregnancy" during the 9 months of pregnancy and resume Botox if desired after your child is born. Good luck and be well.