How effective is IVIg for treating recurrent miscarriage?

IVIG has been involved in many studies for recurrent miscarriage, not all of them showed a positive outcome. Ed Winger in his study showed that it improves the live birth rate to 50%, and many others say it should improve the outcome. But the reviews showed that if you give the IVIG to a selected patient with immune system imbalance, not any patient, and if you give it before pregnancy happens, you can see the outcome. If you give it to old patient with miscarriages, regardless of the cause, obviously you will not see a significant result, and if you give it after pregnancy happens, it's likely to show no benefit. Now, there are some mistakes in previous studies, actually many studies, who gave IVIG to old patients who have miscarriages, obviously you don't expect that one drug will treat all the causes. Not only that, but some famous studies excluded patients with immune issue because the study design was to give IVIG to unexplained recurrent miscarriage. So all the patients who have immune issues were excluded from the study. If you give IVIG, which is an immune [regulatory] drug, to patients who do not have immune issues, what do you expect? You don't expect to have a positive outcome, would you?