Fetal morphological features and abnormalities associated with equine early pregnancy loss

Pregnancy loss in early gestation (EPL) occurs in approximately 8% of equine pregnancies, although the aetiology is mostly unknown and fetal morphological abnormalities associated with early abortions are not defined. The data here were used (i) to compare the macroscopic and histological morphology of EPL to clinically normal fetuses and developmental milestones described in the literature and (ii) to identify morphological abnormalities associated with equine EPL. Clinically normal fetuses (n = 11) were obtained from thoroughbred and pony broodmares and EPL fetuses (n = 27) from thoroughbred mares suffering pregnancy failure. The crown-rump length (CRL) of fetuses was measured and the macroscopic morphology and developmental age determined independently by three blinded examiners, using a standardised protocol. A representative subset of sagittal sections of fetuses was assessed microscopically.