Influence of litter size (number of fetuses) on morphological characteristics of the placenta and the relationship with neonatal development in dogs

Abstract

The placenta is a transitory maternal-fetal organ, responsible for allowing gas exchange between the maternal and fetal circulation in euteric animals, in addition to being the means of passage of nutrients to the fetuses during intrauterine life. Knowing the placental morphology allows the identification of pathological changes and the possible relationship with neonatal viability. It is believed that the number of fetuses per pregnancy may influence fetal-neonatal development due to placental insufficiency or inability to uniformly meet all fetal requirements, resulting in fetuses with intrauterine growth restriction and, later, offspring with reduced growth rate. Therefore, the present study aims to evaluate the influence of litter size on neonatal development and performance in the first two weeks of life and to evaluate the influence of morphological characteristics of the placenta on the vitality, body development and morbidity and mortality rate of puppies during the neonatal period. For this purpose, 10 bitches and 20 neonates will be selected, which will be allocated into two experimental groups: Numerous Litter Group (n=5 bitches; n=10 puppies; females with a higher number of fetuses than the racial reference) and Normal Litter Group (n=5 bitches; n=10 puppies; average number of puppies for breed reference). Will be used, 2 pups of each female submitted to cesarean section and the placentas will be obtained and the zonal band of the placenta will be weighed, measured in width and length and will pass through the immersion test to determine the total placental volume. The placentas will be evaluated for their general appearance and color, especially the regions of the placental labyrinth, marginal hematomas and zonal band. To obtain the influence of fetal weight on placental mass, we will obtain a percentage variable (%) of the ratio of placental weight (g) to offspring weight at birth (g). Then, the zonal range will be submitted to stereological processing for morphological and morphometric evaluation. Newborns will be classified according to viability (alive or stillborn) and, simultaneously with stimulation, will be evaluated by physical examination, using the neonatal vitality score at birth, at 10 and 60 minutes of life. Em momentos pré-estabelecidos após o nascimento, cada neonato será avaliado quanto às seguintes variáveis experimentais: biometria corpórea, lactatemia, oximetria e ganho de peso corpóreo. A biometria e pesagem neonatal serão realizadas aos 60 minutos de vida, após 10 e 14 dias, por 3 medições: altura de cernelha, comprimento corporal, perímetro torácico e pesagem. Para as variáveis dependentes do porte das matrizes (peso da placenta, dimensões placentárias e peso corpóreo neonatal), será feito cálculo de normalização. As variáveis serão analisadas por medidas repetidas no tempo e teste T Student, com nível de significância será de 5%. (AU)