When can I start maternity leave

Sa

Just wondering if anyone knows this or knows who I can call to get an answer. I do not plan on returning to work after this baby. Does anyone know the earliest that I can legally take my maternity leave. My company offers 6 weeks at 50% pay. I have read that you can take it as early as 15 weeks before due date and 11 weeks before due date? I have a great relationship with my boss so I plan on giving him plenty of notice but I also would like to leave as early as I can!