Blood thinners while pregnant

When i was 15 i was diagnosed with lupus anti-coagulant and i was put on warfarin for life. my question is what happens if i get pregnant unplanned and im on warfarin? Is there a different blood thinner to take during pregnancy that wont harm the baby? How long in to pregnancy is it ok to be on warfarin?  Em i still able to be a parent one day?