I too have heterozygous FVL. Caitlyn was stillborn at 25w and there was a retroplacental clot (however this can occur after death and may not have been the cause of her dying in utero). The OB thinks there may have been an issue with 2nd phase implantation which occurs around 22w.

I started aspirin 100mg after 2 blood tests that indicated a rising HCG. I was due to commence clexane after a viable foetus was detected on u/s. We have a HB but I also have a small bleed at the site of implantation so I have held off on the clexane until after seeing the OB on Monday.

I believe my Mum has FVL and she delivered 2 children safely without interventions like me but she developed a large blood clot in her leg after my sister was born by c-section.

There are many viewpoints on the use of anti-coagulation in pregnancy. When trying to conceive Caitlyn we were told by an IVF specialist that they wouldn't consider aspirin and clexane due to my heterozygous FVL alone (despite previous miscarriages). Now, I think they feel it would be negligent NOT to use it considering Caitlyn's loss.

In your situation you need to do some research and ask as many questions as you can such as why do you think it is required now and not at the beginning of the pregnancy?? Informed choice is the only answer to this dilemma and you need to do what is best for you and what you are comfortable with.

Wishing you the best of luck.