Pregnancy loss during the embryonic period

Abstract

Demise of the conceptus before organogenesis is complete, (approx. 40 d gestation in mares), is termed early embryonic death (EED). Many factors affect embryo viability. Genetic abnormalities, defective gametes, factors affecting conceptus mobility, asynchrony between the embryo and the uterus, endometritis, nutritional stress, twins and premature regression of the corpus luteum due to uterine pathology or other inflammatory conditions are among the causes of EED. Diagnosis, sometimes aided by laboratory tests, is primarily by ultrasonographic examination. Prevention of EED includes reducing contamination at breeding and treating endometritis to allow establishment of pregnancy. Correction of anatomic defects is necessary. If exogenous progestogen therapy is used, the viability of the pregnancy should be periodically reaffirmed. The present paper reviews the causes and diagnosis of EED in mares, as well as therapeutic and preventative measures to reduce the incidence of EED.