How to Maintain Pregnancy

On some days, “how to maintain pregnancy” seems an elusive goal. In some cases, by the time practitioners recognize that a mare is demonstrating signs of preterm birth, any assistance we can provide is insufficient to allow delivery of a vigorous and healthy foal. Thus, a large component of how to maintain pregnancy is determining when to intervene. Bosh et al (2009) described reproductive performance measures among 1011 Thoroughbred mares in central Kentucky during the 2004 mating and 2005 foaling seasons (Table 1). This study demonstrated a 12.9% pregnancy loss between day 40 of gestation and foaling. This is similar to fetal loss rates between 3 and 10 months gestation found in other studies. In comparison, the human rate of preterm births in the United States in 12.5%. In a review of 3527 aborted fetuses and placentas, stillborn foals or foals that died 24 hours after birth, 34% were due to feto-placental infection or placentitis of unidentified etiology. Bacterial infection caused 628 (17.8%) of these losses. Complications of birth led to the demise of 679 (19%), congenital anomalies including contracted foals counted for 348 (10%), and no diagnosis was identified in 585 (17%) of these cases. Other causes included placental edema, premature placental separation, twins, umbilical cord anomalies, placental villous atrophy, body pregnancy, fetal diarrhea, and neoplasia. This tells us that if we can manage inflammation and infection, we are targeting approximately one-third of the problem. The vast majority of pregnancies will require no intervention. For anxious clients or mares at higher risk for problematic pregnancy, routine monitoring can be instituted. Case selection can be based on the following: