you should be thankful that your wife can get pregnant.

some people cant even get pregnant.

about miscarriage, thats another issue.

3 times miscarriage? all 3 during 8 to 10 weeks?

besides the chromosomal defect or the chromosome incompatibility between you and wife, there are other things that you can work on.

make sure ur wife dont do heavy / stressful work. No heavy lifting. especially in the early stages, until 2nd trimester then more or less safer.

Metformin is for diabetes? Im sure if doc give it, its safe for pregnancy.

Your wife can take other supplements to help embryo "stick" and grow.
My wife used IBERET (it contains folic acid, very important. plus other things to have a healthy pregnancy)

also for the baby and mom, she also take Calcium with vit d3 and Fish Oil.