miscarriage is only present if you DON'T take Lovenox. The best thing you can do once diagnosed with a clotting disorder is to be correctly anticoagulated and you are taking Lovenox for a diagnosed thrombophilia which can only be a good thing.
You need a good placental blood flow to your embryo and that is what Lovenox will do for you - it counteracts the tendancy to overclot which your diagnosis will cause if it is left untreated.
Please rest assured that Lovenox is a tried and tested regime for your diagnosis and can only help.
Once you get pregnant, you need to be monitored via blood test to make sure that the Lovenox is effective. This can be monitored via your RE or ObGyn.