The purpose of this study is to determine whether Cyclosporin A (CsA) - an immunosuppressant drug - in early pregnancy will reduce the risk of miscarriage in women who had a history of unexplained recurrent miscarriages, as compared with that treated with Dydrogesterone-an active comparator. The hypothesis is based on the evidence found in vitro and in vivo experiments that CsA can induce maternal-fetal tolerance so that it may reduce the risk of miscarriage.