Herpesviral infections frequently occur in horses. The objective of this study was to investigate the possible association of equine herpesviruses (EHV-1, EHV-2, EHV-3, EHV-4, EHV-5) with other causes of abortion, neonatal mortality or placental disorder. Sixty-seven abortions, 22 stillbirths, 14 cases of neonatal foal mortality and 3 cases of placental disease were investigated for infectious and non-infectious causes. Type-specific nested PCR assays and virus isolation were performed to detect EHV infections. A cause of fetal loss or placental disease was reached in 68 out 116 (58.7%) cases. Twenty-seven cases were positive for EHV, and 22/27 (81.5%) were positive for EHV-1 (16 neuropathogenic and 6 non-neuropathogenic strains), 4 (14.8%) for EHV-2 and 3 (11.1%) for EHV-5. The association between EHV infections and other etiological agents was statistically significant (two sided P = 0.002). The odds ratio of EHV DNA associated with other diagnoses, especially with bacterial infection and premature placental separation, was 10.88 (95% confidence interval: 2.15-55.16). EHV-1 was the main viral cause of pregnancy loss in this study, also associated with other etiological agents, including EHV-2 and EHV-5. The latter viruses in particular need to be more fully investigated to elucidate what role either or both may play as co-infecting agents with other established infectious causes of reproductive disease.