Abnormal pregnancies associated with deviation in progestin and estrogen profiles in late pregnant mares: A diagnostic aid

Steroids in the establishment and maintenance of pregnancy and at parturition in the mare

“…As noted earlier, progestational support of pregnancy in mares is complex, and the progestins that appear responsible for maintenance of pregnancy during the second half of gestation are products of the foeto-placental unit. Monitoring peripheral concentrations of progestins in the late pregnant mare has been used for many years as a potential method to assess the well-being of the equine foetus , Ousey 2006, Morris et al 2007, Shikichi et al 2017. This effort has been confounded by the use of progesterone immunoassays with varying cross-reactivity across the spectrum of pregnanes, some in very high concentrations, present in the pregnant mare (Wynn et al 2018b).…”

“…Oestrogens are also products of the foeto-placental unit in equine pregnancy and thus maternal concentrations of various oestrogens and their sulfoconjugates have been measured as a means of assessing foetal well-being or foetal loss (Kasman et al 1988, Hyland & Langstrom 1990, Canisso et al 2017, Shikichi et al 2017. Changes in concentrations of oestrone sulphate in maternal circulation may be less predictive of foetal loss later in gestation (Canisso et al 2017) possibly because of their high circulating concentration at this stage (Legacki et al 2019) and because of their relatively longer halflife.…”

“…Changes in concentrations of oestrone sulphate in maternal circulation may be less predictive of foetal loss later in gestation (Canisso et al 2017) possibly because of their high circulating concentration at this stage (Legacki et al 2019) and because of their relatively longer halflife. However, in general, a decline in 17β-oestradiol in maternal circulation has been associated with mares at risk of abortion in clinical studies (Shikichi et al 2017) as well as in mares with experimentally induced placentitis (Canisso et al 2017) during mid-to-late pregnancy. This is consistent with recent observations in mares with experimentally induced placentitis in which concentrations of oestrone and expression of CYP19A1 in the chorioallantois are both reduced, suggesting that placental synthesis of oestrogens may be negatively impacted by infection or the associated inflammation (El-Sheikh Ali & Ball unpublished data).…”

Factors affecting the prognosis for uterine torsion: the effect of treatment based on measurements of serum progesterone and estradiol concentrations after surgery

“…These reports suggested that the survival rates at <320 days gestation are higher than those at ≥320 days [ 2 , 12 ]. On the other hand, Shikichi et al suggested that measurements of serum progesterone (P 4 ) and estradiol (E 2 ) were useful indicators in management of pregnant mares during late-term gestation [ 11 ]. We have also previously suggested that using serum P 4 and E 2 measurements can be useful for pregnancy management after colic surgery.…”

“…P 4 was determined to be abnormal when exceeding 5ng/m l until Day 300 according to cutoff values reported by Shikichi et al . [ 11 ]. In the CLEIA method, serum P 4 and E 2 concentrations in case 7 were directly measured by end-point assay using anti-progesterone and anti-estradiol antibodies.…”