OBJECTIVE To determine whether the miscarriage rate in recurrent miscarriage patients with an abnormal karyotype, especially reciprocal translocations, in either partner is worse than without an abnormal karyotype. METHODS Retrospectively analyzed prospectively obtained database. METHODS Nagoya City University Hospital. METHODS One thousand and two hundred eighty-four couples with a history of 2 or more (2 to 12) consecutive first-trimester miscarriages. METHODS Patients with antiphospholipid antibodies were treated with low-dose aspirin and combined therapy. METHODS Subsequent miscarriages were compared for cases with and without an abnormal karyotype in either partner. A karyotype analysis was also conducted for each aborted conceptus and offspring of 95 pregnancies of 47 patients with reciprocal translocations. RESULTS Of the total of 1,284 couples, 58 (4.5%) had translocations, 11 being Robertsonian translocations. Eleven of the 18 cases (61.1%) where the husband had a reciprocal translocation suffered further miscarriage; this also was the case for 21 of the 29 cases (72.4%) where the wives had a reciprocal translocation. Those with reciprocal translocations in either partner miscarried significantly more frequently than those without an abnormal karyotype. Only one infant with an unbalanced translocation was found in 34 cases of successful pregnancy following habitual abortion. CONCLUSIONS The pregnancy prognosis with either maternal or paternal reciprocal translocations is poorer than without them. The presence of a reciprocal translocation is thus a risk factor in couples who have recurrent miscarriages.