Patterns of conceptus development and of progesterone concentrations in maternal blood preceding spontaneous early pregnancy failure in mares

Abstract

Sixteen cases of spontaneous pregnancy loss (11 of singletons and five of pairs of twins) are described. The losses occurred between gestation Days 13 and 25 in 12 mares being monitored almost daily by transrectal ultrasonography (for measurement of conceptus growth) and blood sampling (for determination of maternal plasma progesterone concentrations as evidence of luteolysis) in experimental studies of early pregnancy. In 10 of the 16 cases the uterus was flushed and eight conceptuses were recovered for morphological assessment. Five of the 11 losses of singletons occurred before Day 16 and, with one exception, were preceded or accompanied by luteolysis. The remaining six singleton pregnancies failed after Day 16, with two cases evidencing luteolysis beforehand. Thus, overall, 6/11 singleton losses were associated with luteolysis while 5/11 were not. The five cases of simultaneous loss or degeneration of twin conceptuses all occurred on Day 19 or 20, preceded by luteolysis in only one case. These observations suggest that while the causes of spontaneous early pregnancy failure are multifactorial, luteolysis might contribute to the problem more often than has been previously contended.

Transcriptional profiling of equine endometrium before, during and after capsule disintegration during normal pregnancy and after oxytocin-induced luteostasis in non-pregnant mares

“…The mares used to provide endometrial samples were maintained in an experimental herd at the Arkell research station of the Ontario Ministry of Agriculture and Rural Affairs principally for studies of early equine pregnancy under conditions approved by the University of Guelph’s Animal Care Committee [ 18 , 32 ]. General aspects of the mares’ breeds and reproductive management have been described previously[ 32 ]; details of special relevance to the present study are that the developmental stages of samples (relative to the time of ovulation) were known to within ± 0.5 days and that samples of endometrium were retrieved by transcervical biopsy using a pulling biopsy punch (Lane Medical Co., Boulder, CO, USA) as described by Kenney [ 33 ]. Immediately after collection, samples were each divided into three pieces, one was fixed for histology while two were transferred to individual dry cryovials, flash-frozen in liquid nitrogen and stored at -80°C pending isolation of RNA.…”

“…To obtain day-20 endometrium from non-pregnant mares with extended luteal function (so that transcriptomes of pregnant and non-pregnant mares at Day 20 could be compared), 13 mares which had not been inseminated were treated between Days 7 and 14 by daily intramuscular injections of 60 IU oxytocin in the expectation that the luteal phase of their estrous cycles would be extended in 60–70% of cases [ 34 ]. Daily jugular blood samples, drawn, processed and assayed as previously described [ 32 ] were used to distinguish retrospectively between mares in which the luteal phase had or had not been extended up to the time of collection of endometrial samples (8/13 oxytocin-treated mares had extended cycles, 5/13 did not). Extension of luteal phase was determined based on the plasma progesterone values being greater than 2 ng/ml.…”

The use of progestins in equine medicine: A review

“…Deficient progesterone concentrations have been found incompatible with maintenance of pregnancy, but there is limited data to support a primary failure of the CL as a cause of embryonic loss in the horse, and this may be due to the differing types of implantation and placentation (Irvine et al 1990). Interestingly, the laboratory of Betteridge et al (2018) recently described an unexplained decrease in serum progesterone concentrations to supersede early embryonic loss in a subset of mares. In this study, mares were monitored daily via transrectal ultrasonography and daily progesterone measurements.…”

“…Interestingly, the laboratory of Betteridge et al . (2018) recently described an unexplained decrease in serum progesterone concentrations to supersede early embryonic loss in a subset of mares. In this study, mares were monitored daily via transrectal ultrasonography and daily progesterone measurements.…”

>b<Efeito da suplementação hormonal com progestágenos em éguas prenhes sobre os hormônios tireoidianos e esteroides dos neonatos>/b<

“…Em estudos mais antigos, como o de Irvine et al (1990), a concentração de progesterona da grande maioria das éguas que não se mantiveram prenhez (82%) até os 42 dias pós inseminação não caiu até que a perda embrionária de fato ocorresse (BERGFELT; WOODS; GINTHER, 1992). Somente uma das éguas teve queda de progesterona anterior a perda embrionária, sugerindo que a falha luteal não foi a causadora das demais perdas (IRVINE et al, 1990 Ainda assim, há controvérsias sobre o quanto a perda embrionária precoce pode ser diminuída ao se utilizar progestágenos (BETTERIDGE et al, 2018).…”