Even if the regulations came into force as soon as the House made them, they define the period in question as the period that starts on the day of the child's birth or the day when the child is placed with the member for the purpose of adoption, depending on the case, and ends 12 months later. If, at the time of the regulations coming into force, the child has already been born, that 12-month period would have already begun and would continue. The 12-month period would not begin on the date the regulations are made.
On June 6th, 2019. See this statement in context.