Retrospective examinations of 8,139 placentae were performed to clarify the relationship between placental disorders with massive intervillous fibrin deposition (MIFD) and intrauterine growth retardation (IUGR). Although the incidence of MIFD was low (0.4%), the small-for-date (SFD) birth rate in the MIFD group was significantly higher than that in the control group (62.9 vs. 8.3%; p < 0.001). Seventeen of 35 patients in the MIFD group had no clinical complications. MIFD itself was thought to be the main cause of IUGR in these patients. 78.4% of multiparae in the MIFD group gave unsuccessful obstetrical histories such as intrauterine fetal death and fetal growth retardation. Four of 6 patients with a history of MIFD and SFD delivery in a previous pregnancy repeated the same episode. These data indicate the MIFD recurrence rate in subsequent pregnancies must be high. Patients with a history of both SFD delivery and MIFD in previous pregnancies were defined as high-risk patients and they were given orally 30 mg of aspirin and 150 mg of dipyridamole daily and/or daily intravenous injection of 10,000 IU heparin during pregnancy. As a result, MIFD did not recur in all cases of the treated group and 87.5% (7/8) of the treated group could deliver approximate-for-date infants compared with 33.3% (2/6) of the untreated group (p < 0.05). These results indicate that anticoagulant and antiplatelet therapies are extremely effective for prevention of MIFD and IUGR due to MIFD.