I know that you can't usually start mat leave untill 11 weeks before your due date, however I'm hopefully expecting twins and depending on whether they have their own placentas or our sharing (which I'll find out in a few days time) the actual delivery will either be 37 weeks or "lucky to get to 35". Does this affect when I can start my maternity leave or am I bound by a due date which is a minimum of 3 weeks past the latest date they'll be here?