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Uterine haemodynamics in young and aged pregnant mares measured using Doppler ultrasonography.
Abstract: Aged mares with endometrosis suffer higher rates of pregnancy loss than young mares, due to poor placental development. Reduced uterine blood supply may be one contributory factor. Objective: To measure uterine artery (UA) blood flow and other Doppler indices throughout pregnancy and compare placental and foal development in young mares and aged mares. Methods: Thoroughbred mares were grouped according to age and endometrial biopsy score: 1) 6 young mares (mean age 7.3 years, Category ); 2) 6 aged mares (mean age 18.3 years, Category II). Vascular pathology was nil or mild except in one aged mare with moderate perivasculitis. Both UA were scanned fortnightly throughout pregnancy. Total blood flow volume (BFV, ml/min/kg bwt), peak systolic velocity (PSV, cm/s) and resistance index (RI) were determined by pulsed wave, Doppler ultrasound and UA diameter using B-mode. Mixed-effects regression analyses were used to relate vascular parameters with different predictive variables, whilst accounting for the multiple repeated measurements taken from individual horses through the duration of their pregnancies. Results: PSV, RI and total BFV were best predicted by stage of pregnancy (P 78%). The UA diameter was also associated with stage of pregnancy (P < 0.001; r2 = 87%) and was significantly greater in the gravid horn (P < 0.001). There was a tendency for lower total BFV in older mares (P < 0.05) and they delivered lighter foals than young mares (P < 0.05). Gross placental morphometry was similar, but microscopic surface density of the microvilli was lower (P < 0.02), in aged than young mares. Conclusions: Increased uterine blood flow and decreased vascular resistance reflect fetal growth and development of the placental microcirculation. Older mares have poorer placental microvillus development and lighter foals with reduced UA blood flow. Poor uterine blood flow may be an important contributory factor for pregnancy loss in aged mares.
Publication Date: 2012-05-19 PubMed ID: 22594020DOI: 10.1111/j.2042-3306.2011.00446.xGoogle Scholar: Lookup The Equine Research Bank provides access to a large database of publicly available scientific literature. Inclusion in the Research Bank does not imply endorsement of study methods or findings by Mad Barn.
- Journal Article
- Research Support
- Non-U.S. Gov't
Summary
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This study investigates the connection between the age of pregnant mares and the blood flow to their uterus, using Doppler ultrasonography. The findings suggest that reduced uterine blood flow in older mares, which can result in poor development of the placenta and lighter foals, may be a significant factor contributing to higher rates of pregnancy loss.
Methodology
- Thoroughbred mares were divided into two groups: 6 young mares with a mean age of 7.3 years (Category I), and 6 older mares with a mean age of 18.3 years (Category II).
- The uterine blood flow was examined using Doppler ultrasound every two weeks throughout pregnancy.
- Parameters such as blood flow volume (BFV), peak systolic velocity (PSV), resistance index (RI), and uterus artery diameter were assessed.
- To analyse these measurements and link them to predictive factors, mixed-effect regression analyses were employed, taking into account repeated measurements from each mare during their pregnancy.
Findings
- Stage of pregnancy was found to be the best predictor for parameters such as PSV, RI, and total BFV.
- The uterine artery’s diameter was also observed to be linked with the stage of pregnancy, with the artery being significantly wider in the pregnant horn.
- Old mares exhibited a tendency for lower total BFV and delivered lighter foals compared to younger mares.
- While the gross lack of placental morphometry was observed to be similar, older mares were found to have a lower surface density of microvilli, which are small hair-like projections enhancing the placenta’s efficiency.
Conclusion
- The study concludes that an increased blood flow to the uterus and a decrease in vascular resistance are key factors for the proper growth of the fetus and the development of the placenta’s microcirculation.
- Older mares reported less microvillus development in the placenta, which resulted in lighter foals. Additionally, these mares displayed reduced blood flow in the uterine artery.
- The findings suggest that poor uterine blood flow might be a significant factor contributing to the higher rates of pregnancy loss observed in older mares.
Cite This Article
APA
Ousey JC, Kölling M, Newton R, Wright M, Allen WR.
(2012).
Uterine haemodynamics in young and aged pregnant mares measured using Doppler ultrasonography.
Equine Vet J Suppl(41), 15-21.
https://doi.org/10.1111/j.2042-3306.2011.00446.x Publication
Researcher Affiliations
- The Equine Fertility Unit, Mertoun Paddocks, Newmarket, Suffolk, UK. jousey@waitrose.com
MeSH Terms
- Aging / physiology
- Animals
- Female
- Hemodynamics / physiology
- Horses
- Pregnancy
- Pregnancy Outcome
- Pregnancy, Animal / physiology
- Ultrasonography, Doppler / veterinary
- Uterine Artery / physiology
- Uterus / blood supply
Citations
This article has been cited 3 times.- Abdelnaby EA, Emam IA, El-Sherbiny HR, Fadl AM. The effects of aging and gestational month on uteroplacental vascular perfusion, and umbilical artery hemodynamics in pregnant jennies. BMC Vet Res 2022 Nov 15;18(1):404.
- Sharman P, Young AJ, Wilson AJ. Evidence of maternal and paternal age effects on speed in thoroughbred racehorses. R Soc Open Sci 2022 Oct;9(10):220691.
- Santos VJC, Rodriguez MGK, da Silva PDA, Mariano RSG, Taira AR, Padilha-Nakaghi LC, Uscategui RAR, Feliciano MAR, Oliveira MEF, Moraes PC, Vicente WRR. Assessment of dopperfluxometric indices of maternal-fetal structures in pregnant ewes. Anim Reprod 2021;18(2):e20210002.
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