Pregnant Pigs at Slaughter-An Overview of Legal and Ethical Frameworks, Reasons, Occurrence, and Fetal Age Determination.

The slaughter of pregnant pigs raises legal, ethical, and animal welfare concerns in pig production. Relevant information for this overview was compiled from research identified through searches of PubMed, Web of Science, and Google Scholar using defined combinations of search terms related to pregnancy, slaughter of sows, fetal age, gestational stage, and prevalence. No lower time limit for publication year was predefined; publications published up to 2025 were considered. Regulations vary widely between countries, with some specifying clear restrictions for animals in late gestation, while many provide no stage-specific limits. Reasons for culling include economic pressures, management practices such as unrecognized pregnancies and mixed-sex housing, and health or welfare issues. In Europe, the prevalence of sows being pregnant at slaughter ranges from 1.5% to 13%, with most fetuses being in the first or second trimester and a small proportion in the final trimester. In Africa, prevalence is higher and more variable, ranging from 9% to 36.14%, with a larger share of fetuses in mid to late gestation. Data from America is limited, reporting prevalences between 5.9% and 13.5%. The comparability of prevalence estimates is limited due to high heterogeneity and differences in study design. Fetal age can be assessed using metric or non-metric methods, applied either postmortem or in vivo (for example, ultrasonography). Variations in study design, methodology, and population characteristics restrict direct comparability. For legal enforcement and veterinary inspection, reliable fetal age assessment is important, and updated fetometric reference values could contribute to a more consistent interpretation of fetal age.