Physical Interplay between Equine Fetus and Uterus from Day 180 to End of Pregnancy☆☆.
Abstract: Traveling of the fetal-amniotic unit throughout the uterus ceases on ∼ Day 180 followed by closure of each uterine horn. By mean Day 240, the fetus and nearly all of the pool of allantoic fluid are confined to the uterine body. Intrauterine fetal-location changes end, but in-place activity of limbs, head, and body and changes in fetal recumbency and presentation continue, sometimes vigorously. Preference for cranial presentation (fetal sternum toward maternal cervix) has been hypothesized to be stimulated by ∼ 40° incline of uterine body toward the cervix. The uterine body expands forward, but the closed uterine horns are held more closely at the tips and become perpendicular to the cranial uterine body. After closure of horns, both hind limbs enter the umbilical-cord horn apparently guided by dorsal recumbency (fetal spine toward uterine floor), close proximity of hind hooves to horn entrance, and a thick covering of each main umbilical vessel by Wharton's jelly. The limb-encased horn then begins to lie on the upper surface of the uterine body from flexure of the hind limbs. The active fetal rump may raise off the uterine floor so that the hooves of the hind limbs reach the area above the cervix. Dorsal fetal recumbency is anchored by the horn-encased hind limbs, but when the uterus rests on the mare's ventral abdominal wall, the loosened suspensory ligaments allow more rotational freedom. During parturition, the fetal head and withers twist toward the mare's spine, and the rear follows like a corkscrew.
Copyright © 2022. Published by Elsevier Inc.
Publication Date: 2022-03-04 PubMed ID: 35257827DOI: 10.1016/j.jevs.2022.103918Google Scholar: Lookup
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Summary
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This research explores the physical interactions between a horse fetus and the uterus from the 180th day of pregnancy till birth. It highlights the movements of the fetus within the uterus, changes in its position and the factors that influence such movements.
Understanding the Fetus and Uterus Interaction
The research indicates that after approximately 180 days of pregnancy, the movement of the fetal-amniotic unit within the uterus comes to a halt and the uterine horn closes. Following this:
- The fetus and most of the allantoic fluid become confined to the body of the uterus around the mean 240th day.
- Physical movements of the fetal limbs, head and body persist within the limited space.
- Changes in the fetus’s position continue, with a preference for cranial presentation. This position has the fetus’s sternum directed towards the maternal cervix and is speculated to be motivated by the 40-degree inclination of the uterine body towards the cervix.
- The uterine body expands forward while the closed uterine horns remain static at the tips and become perpendicular to the body of the uterus.
Festal Action and Uterine Adjustments
The report also talks about the steps following the closure of the uterine horns:
- At this point, both hind limbs of the fetus enter the umbilical-cord horn due to factors such as the dorsal recumbency drawing the fetal spine towards the uterine floor, the closeness of the hind hooves to the horn entrance, and Wharton’s jelly covering of the principal umbilical vessels.
- The horn, enclosing the limbs, starts to lie on the uterine body’s upper surface as a result of the flexure in the hind limbs.
- The hind limbs might touch the region above the cervix when the active fetal rump lifts off the uterine floor.
Later Stages and Parturition
Towards the end of pregnancy and during parturition:
- The hind limbs, enclosed by the horn, anchor the dorsal recumbency of the fetus.
- However, when the uterus is resting on the mare’s ventral abdominal wall, the loosened suspensory ligaments provide rotational freedom to the fetus.
- During parturition (birth), the fetus’s head and withers (the highest point on a horse’s back) twist towards the mare’s spine, following which the rear follows in a corkscrew-like manner.
This research enhances current understanding of the physical progression of equine pregnancy and the interactions between a horse fetus and uterus.
Cite This Article
APA
Ginther OJ.
(2022).
Physical Interplay between Equine Fetus and Uterus from Day 180 to End of Pregnancy☆☆.
J Equine Vet Sci, 112, 103918.
https://doi.org/10.1016/j.jevs.2022.103918 Publication
Researcher Affiliations
- Eutheria Foundation, Cross Plains, WI; Department of Pathobiological Sciences, School of Veterinary Medicine, University of Wisconsin-Madison, Madison, WI. Electronic address: oj.ginther@wisc.edu.
MeSH Terms
- Animals
- Cervix Uteri
- Female
- Fetus
- Horses
- Pelvis
- Physical Examination
- Pregnancy
- Uterus
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