Clexane before Transfer

Anyone who did IVF, Frozen or fresh transfer, took Clexane injection?

When i did fresh transfer my doctor didn’t prescribe it for me and i lost my baby at 4w4d,

Now I’ll be doing frozen and im with different doc he told me its optional if i want Clexane or not but he said he always prescribe it for his patients and I agreed and I’ll have to take it for 3 weeks i think it decrease the chance of miscarriage