ANS 536- PERINATOLOGY BY LEAH ELSBERND Uterine Capacity

Outline  What is Uterine Capacity?  Factors affecting uterine capacity (Maternal Constraints)  Maternal size  Maternal age  Uterine Size  Placental Physiology  Parity of mother  Importance of Uterine Capacity in the Animal Industry

 Uterine capacity- the limit in the number and size of conceptus’ mothers can successfully carry to full term Defining Uterine Capacity

Evolutionary History/Significance of Uterine Capacity  Mothers developed mechanisms that prioritize their well-being and survivability over their fetus’.  Evolution must allow for the mammalian fetus to be delivered by a natural vaginal birth, irrespective of the influence of the paternal/fetal genome.

Evolutionary History/Significance of Uterine Capacity  Maternal constraint- used to describe the set of non- genetic and non-pathological influences by which the mother limits fetal growth  Maternal size  Maternal age  Uterine size  Placental Physiology  Parity of mother

Affect Maternal Size Plays on Uterine Capacity  Multiple studies were conducted to decipher whether maternal size correlates with fetal birth weight.  Crossbreeding Shire horses and Shetland ponies 

Affect Maternal Size Plays on Uterine Capacity Continued…  Analyzing the outcome of crossbreeding study  Birth weight is controlled by non-Mendelian genetics that occur through the maternal lines  Fetal growth matches the mother’s physical size  Mother’s with anatomically small bodies do not have the physical capacity to carry a large fetus, so we observe that small mothers have:  Reduced pelvic dimensions = reduced uterine capacity  As a result of reduced uterine capacity, reduced placental size

Another Example Regarding Maternal Size  Average US birth weight between : lbs.  Genetic Potential: Paternal side  8.5lbs, 21” in length  210 lbs, 6’0” (Ave.-Lrg. body frame) Uterine Capacity (Restriction of growth)  Baby (at birth): 7lbs 2oz, 19.5”  Mom: 5’3”, 95lbs (Sml. body frame)  Gained only 25lbs during 9mo. Pregnancy ~25lbs total gain – (~7lbs fetus+~7lbs placenta)= 11 lbs. extra. No more room for fetus to grow!

Effects Maternal Age has on Uterine Capacity  It is commonly seen that pregnant adolescents have offspring with lower birth weights and smaller size than pregnant adults.  Period of adolescence (Ages 10 to 19)-Rapid growth  Adolescences have a reduced resistance to anabolic effects of somatogenic hormones made by the placenta  Increased risk of IUGR and preterm birth

Effects of Uterine Size on Uterine Capacity  In a study done at the University of Nebraska, they researched the litter size of sows.  They used Superovulation and Superinduction  Superovulation- mother shed excess ova  Superinduction- transfer of embryos to an already pregnant uterus  Performed unilateral hysterectomy-ovariectomy on sows varying in gestation.

Effects of Uterine Size  What they found was limitations of uterine capacity began to affect conceptus survival after day 30.

Effect of Uterine Size on Litter Bearing Species.  In mice- larger uterus and increased blood supply increased fetal growth  Inverse relationship between number of fetuses and size

Affect Placental Physiology has on Uterine Capacity  What affects how well nutrients will be transferred from the mother to the fetus?  Shape of placenta  Thickness of placenta  Vascularity of placenta  Density and number of protein transporters on the placenta  Nutrients from the mother need to pass through two layers of syncytiotrophoblasts membranes and the fetal capillary epithelium before they can reach the fetus.

Affect Placental Physiology has on Uterine Capacity  Shape of Placenta- changes surface area  Thickness of Placenta- the ability for nutrients to get across membrane layers

Affect Placental Physiology has on Uterine Capacity  Vascularity of placenta- the vascular architecture of the placenta  Horse vs. human placental efficiency

Affect Placental Physiology has on Uterine Capacity  Availability and number of protein transporters on the placenta

Affect Placental Physiology has on Uterine Capacity  How does placental physiology affect fetal growth?

Affect Parity Has on Uterine Capacity  Comparing uteroplacental vasculature in primparious and multiparous mothers  spiral arteries

Affect Parity Has on Uterine Capacity  Primiparous vs. Multiparous  Depth of Abdominal cavity

Affect Parity Has on Uterine Capacity Stretch of the uterus and birth canal

Affect Parity Has on Uterine Capacity  Virgin Heifers vs. Dairy cows after second calving

Affect Parity Has on Uterine Capacity

So why is Uterine Capacity Important?  The animal industry strives to be productive while keeping in mind the welfare of the animals.  Therefore, reducing dystocia is a main goal  Increases fetal and maternal survivability at birth

Issues the Dairy Industry is Facing  Calf loss due to dystocia in the dairy industry is responsible for 125 million dollars of lost revenue every year  Research Findings:  18.98% of primiparous Holsteins experienced dystocia  5.73% of primiparous Jerseys experience dystocia

Attempt to Combat Dystocia in the Dairy Industry  Crossbreeding  Selecting low birth weight bulls  Diet

Sources Ford, S. P., Vonnahme, K. A., and Wilson, M. E. "Uterine capacity in the pig reflects a combination of uterine environment and conceptus genotype effects." Journal of animal science 80.E-Suppl_1 (2002): E66-E73. Gluckman, Peter D., and Mark A. Hanson. "Maternal constraint of fetal growth and its consequences." Seminars in fetal and neonatal medicine. Vol. 9. No. 5. WB Saunders, Walton, Arthur, and John Hammond. “The Maternal Effects on Growth and Conformation in Shire Horse-shetland Pony Crosses”. Proceedings of the Royal Society of London. Series B, Biological Sciences (1938): 311–335. Wells, Jonathan C. K. et al. “Paternal and Maternal Influences on Differences in Birth Weight between Europeans and Indians Born in the UK.” Ed. Hamid Reza Baradaran. PLoS ONE 8.5 (2013): e PMC. Web. 4 Apr Fowden, A L et al. “Placental Efficiency and Adaptation: Endocrine Regulation.” The Journal of Physiology 587.Pt 14 (2009): 3459–3472. PMC. Web. 5 Apr Lyall, Fiona et al. “Human Trophoblast Invasion and Spiral Artery Transformation: The Role of PECAM-1 in Normal Pregnancy, Preeclampsia, and Fetal Growth Restriction.” The American Journal of Pathology (2001): 1713–1721. Print. R. Pijnenborg, L. Vercruysse, and M. Hanssens, “The uterine spiral arteries in human pregnancy: facts and controversies,” Placenta, vol. 27, no. 9-10, pp. 939–958, Olson, K M; Cassell, B G; McAllister, A J; Washburn, S P. "Dystocia, stillbirth, gestation length, and birth weight in Holstein, Jersey, and reciprocal crosses from a planned experiment." Journal of Dairy Science. American Dairy Science Association HighBeam Research. 8 Apr Dystocia, stillbirth, gestation length, and birth weight in Holstein, Jersey, and reciprocal crosses from a planned experiment." Journal of Dairy Science. American Dairy Science Association HighBeam Research. 8 Apr <

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