Hi Arubagirl,
I have thalassemia minor, and during my second pregnancy, my hg also fell to levels similar to yours. The prolonged anemia during my pregnancy caused my spleen to enlarge and I felt exhausted. I also had placenta previa, and was at high risk of bleeding - so I was transfused once during my pregnancy. I was a lot more energetic after the transfusion, and much better able to take care of my son. My hg held very well after the transfusion, so I did not require another one.
I think that part of the reason the hg seems lower during pregnancy is that the blood volume increases and the hg appears a little lower, the other may be the pregnancy taxing the body - using up more hg.
I was lucky to have had the transfusion because my placenta did tear at 36 weeks, and I did bleed quite a bit. After the c-section my hg was 70.
As you are carrying twins, and it is earlier in your pregnancy I think it is wise to get the transfusion. I am glad that I did. Best of luck!!
Sharmin