Almost all of our sows are giving dead piglets , what can be the possible reasons and how to resolve it.
Outside United States
It sounds like a disease problem or could be moldy feed. A veterinarian is essential to get a proper diagnosis. Most swine producers give a pre-breeding vaccination for reproductive diseases like Leptospirosis or Parvovirus (PPV). Descriptions of disease can be found at the Iowa State Vet college web site: https://vetmed.iastate.edu/vdpam/FSVD/swine/index-diseases
Here is a site that will help your veterinarian decide how to diagnose and treat your problem, assuming no swine experience: http://www.thepigsite.com/pighealth/article/134/diseases-affecting-reproduction/