Measurement of progestines and estrogens in maternal plasma has been advocated as an indicator of foeto-placental function. The goals of the present study were as follows: to determine progestin and estrogen concentrations in mares with normal and abnormal pregnancies during late gestation, evaluate the diagnostic value of hormone concentrations, and investigate the relationship between hormone concentrations after treatment and the survival of foals. Blood samples were collected monthly from 459 pregnant mares between Day 201 of gestation and foaling. Progestin and estrogen concentrations were measured using a time-resolved fluoroimmunoassay with anti-progesterone and anti-17β-estradiol antibodies. The cutoff values of hormone concentrations that best discriminated between healthy foals and foal loss groups were determined using receiver-operating characteristic (ROC) curve analysis. Mares with compromised pregnancies are treated with progestins, tocolytics and antibiotics according to clinical signs, ultrasonographic examination and hormonal test. We investigated the relationship between the restoration of hormone concentrations after treatment and the survival rate of the foals of 62 compromised mares. Maternal serum progestin and estrogen concentrations on Days 241-320 of gestation differed significantly between healthy foals and foal loss of each group. Predictions of pregnancy outcomes were based on ROC curve analysis that established cutoff values of serum progestin and estrogen concentrations for each 20-day interval during gestation. All mares with improved concentrations of progestins or estrogens after treatment delivered healthy foals. When hormone concentrations got worse after treatment, the rate of loss was higher when treatment was administered during Days 201-290 of gestation than after Day 290. Mares with high progestin and low estrogen concentrations were likely to deliver aborted/dead foals during mid-to-late gestation. These results suggest that measurement of progestin and estrogen concentrations may be useful for diagnosing abnormal pregnancy and implementing early treatment strategies.
Keywords: Abortion; Cutoff values; Estrogens; Late pregnancy; Mare; Progestins.
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