Project snapshot: The equine fetal membranes: What is normal? A study of the gross and histologic appearance of the equine fetal membranes from thoroughbred foalings

The Australian thoroughbred breeding industry generates almost $1.68 billion each year and produces more than 12,000 foals. However, pregnancy loss remains a major challenge. Many abortion and stillbirth cases still have no clear cause. This creates costs for breeders and limits prevention efforts.

To help address this gap, researchers studied fetal membranes from 100 healthy thoroughbred foalings during the 2023 breeding season. The aim was to define what normal fetal membranes look like and to provide reliable reference data for veterinarians and pathologists.

The study examined membrane appearance, tissue structure, inflammatory cells and immune cells. Researchers found that several features often considered abnormal can occur in healthy pregnancies. For example, colour and texture changes appeared in 3% to 23% of cases. Placental Areas of Degeneration also occurred in 37% of normal foalings.

The research showed that the widely used ‘1-2-3 rule’ for foaling times does not fit every healthy mare and foal. Many normal foals took longer than two hours to nurse.

Researchers also established baseline counts for inflammatory cells. They also identified a normal immune profile dominated by T-lymphocytes, while B-lymphocytes were absent.

These findings provide clear benchmarks for diagnosing disease. They support more accurate assessments, better reproductive outcomes, improved mare and foal health, and lower losses across the Australian equine breeding industry.

Read the full report here.