Luteal Phase Defect (or Defecit, I've heard it both ways) It's when your luteal phase is super short (less than 10 days) so the embryo doesn't have enough time to implant itself, you can have chemicals but it's highly unlikely you can get past that 10 day mark. There's a bunch of causes like low progesterone or not maturing your follicles or having weak follicles.