1. Department of Obstetrics and Gynecology (S.Y., K.N., Y.O., T.M.), Gunma 371-8511, Japan
2. CREST (K.N., T.M.), JST (Japan Science and Technology), Japan
3. Department of Clinical Laboratory Medicine (K.T., M.M.), School of Medicine, Gunma University, Gunma 371-8511, Japan