The purpose of this thesis is to provide a critical analysis of research findings about nonpharmacological techniques used independently of pharmacological techniques to prevent or reduce procedural pain for infants in the neonatal intensive care unit (NICU). A synthesis of the current research related to nonpharmacological pain relief techniques for infants was conducted for this thesis. Nonpharmacological interventions reviewed in this study include: Kangaroo Care, swaddling, facilitated tucking, positioning, music, non-nutritive sucking and sucrose. An interdisciplinary review of the research was performed using the interdisciplinary databases Cumulative Index of Nursing and Allied Health, PubMED, and PsychINFO. Inclusion criteria for this thesis consists of research focused on preterm neonates (born less than] 37 weeks gestational age) in the neonatal intensive care unit, the use of nonpharmacological interventions for procedural analgesia, peer reviewed articles, and those written in the English language. This study excludes full term neonates due to the significant number of preterm neonates in the NICU. A total of 18 studies were included in this review. All interventions except for positioning show statistically significant evidence to support their use to reduce procedural pain in preterm neonates. Findings of this thesis may promote further studies and exploration into this field. In addition, this thesis establishes the role of the nurse in providing pain relief for infants in the NICU, as well as provide for enhancement of interdisciplinary care amongst other health care providers.

Introduction: Sepsis is a major source of morbidity and mortality in neonates; however, identification of the causative pathogens can be challenging. Next generation sequencing (NGS) is a high-throughput, parallel sequencing technique for DNA. Pathogen-targeted enrichment followed by NGS has the potential to be more sensitive and faster than current gold-standard blood culture. In this pilot study, we will test the feasibility and pathogen detection patterns of pathogen-targeted NGS in neonates with suspected sepsis. Additionally, the distribution and diagnostic accuracy of cell-free DNA and protein C levels at two time points will be explored. Methods: We will conduct a prospective, pilot observational study. Neonates over 1 kg with suspected sepsis from a single tertiary care children’s hospital will be recruited for the study. Recruitment will be censored at 200 events or 6 months duration. Two blood study samples will be taken: the first simultaneous to the blood culture (time = 0 hr, for NGS and biomarkers) via an exception to consent (deferred consent) and another 24 hours later after prospective consent (biomarkers only). Neonates will be adjudicated into those with clinical sepsis, culture-proven sepsis and without sepsis based on clinical criteria. Feasibility parameters (e.g. recruitment) and NGS process time will be reported. Analysis: NGS results will be described in aggregate, compared to the simultaneous blood culture (sensitivity and specificity) and reviewed via expert panel for plausibility. Pilot data for biomarker distribution and diagnostic accuracy (sensitivity and specificity) for distinguishing between septic and non-septic neonates will be reported. Study amendment and interim results: After obtaining ethics approval, study enrolment started October 15, 2020. Interim feasibility results showed successful deferred consent, but low enrolment. A study amendment was used to increase enrolment, create pre-packaged blood kits and implement a substitute decision maker Notification form. / Thesis / Master of Health Sciences (MSc)

This review of literature was conducted to evaluate research on the efficacy of nonpharmacological interventions for use with neonates undergoing minimally invasive skin-breaking procedures. This review primarily focuses on the use of nonnutritive sucking, sweet solutions (such as sucrose, dextrose, etc.), and the synergistic effects of combining these therapies. Research reviewed was limited to peer-reviewed studies written in the English language that evaluated the use of nonnutritive sucking and/or sweet solutions as pain management interventions for neonates (aged 0-1 month) undergoing heel lance or venipuncture. The findings of the studies reviewed support the effiaccy of nonnutritive sucking and the administration of sweet solutions as independent interventions for neonatal pain management, and addditionally indicate that employing these interventions together offers significant synergistic analgesic effects. Further research is required to account for the effects of gestational age and blood-collection method (instrument used) on infant pain. Future studies that focus on the multimodal use of various non-pharmacologic therapies to achieve maximal possible synergistic analgesic effects are indicated. The combined use of nonnutritive sucking and sweet solutions is a simple, inexpensive, effective intervention for managing procedural pain in infants, and nurses should advocate for standardization of this intervention in clinical practice.

In dieser retrospektiven Pilotstudie zum Einsatz von rekombinatem, aktivierten Faktor VII bei Frühgeborenen (Schwangerschaftswoche < 32, Geburtsgewicht < 1750 g) mit intraventrikulären Hirnblutungen wurden anhand sonografischer Untersuchungen der Blutungsprogress sowie die Nebenwirkungen der Therapie im Vergleich zur Standarttherapie mit Fresh Frozen Plasma untersucht. Die Auswertung erfolgte in zwei Gruppen: innerhalb des Gesamtkollektives und innerhalb der Matching-Gruppe. Es zeigte sich in beiden Auswertungsgruppen ein signifikant geringerer Blutungsprogress in der Therapiegruppe. Außerdem konnte ein früherer Blutungsstopp in der Therapiegruppe nachgewiesen werden. Ein erhöhtes Nebenwirkungspotential von rekombinantem, aktivierten Faktor VII war in diesem Patientenkollektiv nicht eruierbar. Weiterführende prospektive, randomisierte, multizentische Studien zur Evaluation dieses vielversprechenden Therapieansatzes werden empfohlen.

La constante augmentation des allergies en début de vie suggère une déficience de régulation immunitaire au cours de cette période. La tolérance orale est un mécanisme clé de régulation au niveau de l’intestin pour le maintien de l’homéostasie immunitaire. L’objectif de ma thèse a été de déterminer dans un modèle murin les mécanismes à l’origine de la tolérance orale en début de vie afin de mieux prévenir le développement d’allergies. L’induction de tolérance orale en début de vie n’est efficace qu’à partir de la 3ème semaine de vie. Le défaut de tolérance orale observé au cours des 2 premières semaines de vie est la conséquence d’un défaut de capture de l’antigène et d’expression de la RALDH (enzyme de conversion du rétinol en acide rétinoïque) par les cellules dendritiques CD103+ mésentériques, résultant en une ignorance de l’antigène. Les taux de rétinol sanguins en période néonatale sont très bas, et un enrichissement du lait maternel en vitamine A permet de corriger cette déficience néonatale ainsi que le défaut de présentation antigénique des cellules dendritiques CD103+. Cet enrichissement permet également de prévenir l’apparition de l’allergie dès les premiers jours de vie. De manière surprenante, alors que chez la souris adulte, la tolérance orale dépend de la génération de lymphocytes T régulateurs, la tolérance orale observée chez les souriceaux âgés de 3 semaines et chez les nouveau-nés ayant reçu de la vitamine A, dépend de la génération de lymphocytes Th1. / Increased prevalence of allergies in early life suggests a deficiency of immune regulation during this period. Oral tolerance is a key immuno-regulatory mechanism in the gut for immune homeostasis. The principal objective of my thesis was to determine in a murine model the mechanisms at the origin of oral tolerance in early life to better prevent allergy development. We found that induction of oral tolerance in early life is effective only from the 3rd week of life. The defect of oral tolerance observed during the first 2 weeks of life is the consequence of a defect in antigen capture and RALDH expression (enzyme which converts retinol in retinoic acid) by mesenteric CD103+ dendritic cells. Serum levels of retinol in neonatal period are very low, and an enrichment of the maternal milk with vitamin A allows to correct this neonatal deficiency as well as the defect of antigen presentation by the CD103+ dendritic cells. This enrichment also allows allergy prevention from the first days of life. To our surprise, while in adult mice, oral tolerance depends on the generation of regulatory T lymphocytes, oral tolerance observed in the 3 week-old mice and in the newborn which received vitamin A, depends on the generation of Th1 lymphocytes. These results demonstrate that vitamin A levels in early life are directly correlated with Th1 differentiation induced by oral administration of allergen, necessary for allergy prevention. This knowledge should now be taken into account for the implementation of allergy prevention strategies, more specific and better adapted to the neonatal period, such as a supplementation with vitamin A.

O período neonatal é marcado por uma maior susceptibilidade a diversas infecções, devido a uma dificuldade de gerar respostas pró-inflamatórias e de perfil Th1. As atividades imunorreguladoras do NO vem chamando a atenção nos últimos anos. Assim, decidiu-se avaliar se o NO era capaz de modular a resposta de neonatos, revertendo esse perfil anti-inflamatório e Th2 característico deste período. Células mononucleares de adultos e neonatos foram isoladas e estimuladas com agonistas de TLR, ou PHA na presença do inibidor de NOS, L-NAME, ou do doador de NO, NOC-18. A nível inato, o uso de L-NAME causou uma menor secreção de citocinas inflamatórias, em ambos os grupos, enquanto que o de NOC-18 não modulou essa secreção. O estímulo com PHA, em conjunto com NOC-18, causou um aumento na secreção de IL-4, IL-2, IL-10 e TNF-&#945; pelas células de adultos. Nos neonatos não houve alteração no perfil de citocinas secretadas, mas houve uma maior ativação dos linfócitos T CD4+. Os dados indicam que o NO pode modular de formas diferentes a resposta imune de adultos e neonatos. / Newborns are more susceptible to infections because their difficulties to develop pro-inflammatory, and Th1 bias responses. NO-immunomodulatory properties have been drawing attention in the last few years. Then, we decided to evaluate whether NO is able to modulate newborn immune responses, reversing this anti-inflammatory and Th2 profile, characteristic of this period. Adult and newborn mononuclear cells were isolated and stimulated with TLR agonists, or PHA in the presence of L-NAME, an NOS inhibitor, or NOC-18, an NO donor. In innate responses, L-NAME decreased pro-inflammatory cytokines release in both groups, however, NOC-18 did not modulate this secretion. PHA stimulus with NOC-18 increased IL-4, IL-2, IL-10 and TNF-&#945; release by adult cells. In neonates there were no change in cytokine release, but there were an increase in T CD4+ lymphocyte activation. Data indicates NO is able to modulate adult and newborn immune responses in different ways.

Resumo: O objetivo deste estudo foi determinar os fatores ambientais que modulam o comportamento materno-filial nas primeiras horas após o parto, período essencial para desenvolver os laços da mãe com o bezerro. Os dados foram obtidos durante sete anos de pesquisa com o rebanho da Estação Experimental de Zootecnia de Sertãozinho, SP, com quatro raças de bovinos de corte: Nelore, Guzerá, Gir e Caracu. No primeiro artigo destaca-se uma análise dos principais fatores ambientais e seus efeitos no comportamento de vaca e bezerro e a relação do comportamento do bezerro com sua sobrevivência até os 120 dias de idade. O segundo artigo mostra as diferenças nos comportamentos exibidos pelas vacas e pelos bezerros da raça Nelore em função da experiência materna e o terceiro trata da descrição de um potencial predador, o urubu (Coragyps atratus) e sua influência no comportamento materno-filial nas primeiras horas após o parto. Nessas três abordagens os principais fatores considerados foram: ano do parto, raça, número de partos da fêmea, local do parto, hora do parto, tempo que a mãe passa em contato com a cria, agilidade do bezerro e presença do predador. Os resultados sugeriram ser necessário acompanhamento mais detalhado dos partos, monitorando as causas que prejudicaram a relação vaca e bezerro e mostraram que a latência para ficar em pé pode ser utilizada como indicador de vigor do bezerro recém nascido. / Abstract: The objective of this study was to determine the environmental factors that modulate maternal-offspring behaviour during the first hours after parturition, period, in which, the bond between mother and calf is developed. The data were recorded during seven years at Estação Experimental de Zootecnia de Sertãozinho, located in São Paulo State, Brazil. Four breeds of beef cattle (Nelore, Guzerá, Gir and Caracu) were studied. In the first article the main environmental factors and their effects upon cow and calf behaviour is analyzed as well as he relationship between calf behaviour and its survival up to 120 days of age. The second article shows behavioural differences of Nelore cows and calves induced by the mother's experience and, finally, the third article is related to the presence the black vulture (Coragyps atratus), a potential predator, at calving site, as well as its influence upon maternal-offspring first hours after the birth. The main factors considered in these three studies were: year of birth, breed, cow's parturition number, birth site, birth time, grooming time devoted of mother to its calf, calf agility and predator presence. These results suggest the need of more detailed birth keep up, monitoring cow and calf relationship's harmful causes. Furthermore suggests that latency so stand up could be used as an indicator of calf vigour. / Orientador: Mateus José Rodrigues Paranhos da Costa / Coorientador: Valter U. Cromberg / Banca: Artur Andriolo / Banca: Alexandre Amstalden Moraes Sampaio / Banca: Evaldo Antonio Lencioni Titto / Banca: João Alberto Negrão / Doutor

O uso profilático dos antimicrobianos é frequente na produção animal para a prevenção de infecções entéricas ou respiratórias de origem bacteriana, contudo, pouco se conhece a respeito do impacto dessa administração. Assim, o presente estudo avaliou o uso profilático de ceftiofur em leitões neonatos sobre a ocorrência de infecções, o desempenho, a frequência de dias com escore fecal alterado e a quantificação de bactérias eliminadas nas fezes na maternidade e na creche. Foram utilizados 174 leitões recém-nascidos divididos em dois tratamentos: Ceftiofur (CEF, 5 mL/kg, n=89) e Controle (CTR, solução salina tamponada, n=85), ambos administrados no primeiro dia de vida e pela via de intramuscular. O delineamento foi em blocos, sendo considerados a ordem de parto e o peso dos leitões como bloco e os dados foram submetidos à análise de variância, empregando-se o programa SAS (2002). O nível de significância considerado foi de 5%. Na maternidade, os leitões tratados com ceftiofur não apresentaram redução na ocorrência de infecções e na eliminação de bactérias nas fezes, assim como não houve maior frequência de escore fecal alterado. Verificou-se um aumento gradativo na eliminação de bactérias até o 14º dia de vida com posterior declínio (P<,0001). Já para o desempenho, os leitões que receberam o ceftiofur apresentaram peso superior aos 21 dias de idade (P=0,0002) e o ganho de peso superior (P<,0001) em relação ao controle. Esta última característica também aumentou com o avançar da idade (P<,0001). Na creche, o tratamento ceftiofur não foi capaz de influenciar a ocorrência de infecções, bem como não interferiu no escore fecal (P>0,005), no desempenho (P>0,005) e na quantificação de bactérias eliminadas (P=0,6833). Conclui-se que a administração profilática de ceftiofur no primeiro dia de vida do leitão não reduziu a ocorrência de infecções, não reduziu a frequência de dias com escore fecal alterado e os leitões não eliminaram menor quantidade de bactérias nas fezes na maternidade e na creche, contudo os leitões apresentaram melhor desempenho durante o aleitamento, mas não na fase de creche / Prophylactic use of antimicrobials is a widespread practice in livestock production as a therapy for enteric or respiratory bacterial infections, however, little is known regarding the consequences of this management. Thus, the aim of the present study was to evaluate the prophylactic use of ceftiofur on the occurrence of infections, performance, frequency of days with altered fecal score as well as the quantification of bacteria excreted through feces of suckling and nursery piglets. For this purpose, 174 newborn piglets were assigned to two treatments as follows: Ceftiofur (CEF, 5 mL/kg, n=89) and Control (CTR, tamponed saline solution, n=85), both administered intramuscularly on the first day of life. The experimental design was in blocks; parturition order and piglet weight was considered as one block. Data were subjected to analysis of variance using the SAS software (2002). At the level of 5% of significance. During the suckling period, piglets treated with ceftiofur showed no reduction in the occurrence of infections and the excretion of bacteria through feces; also the frequency of altered fecal score was unchanged. There was a gradual increase in fecal bacterial excretion until the 14th day of life, declining after this period (P<.0001). Regarding piglet performance, the group treated with ceftiofur were heavier at 21 days (P=0.0002) and had higher average daily gain (ADG) (P<.0001) compared to control. Moreover, ADG traits also increased concomitantly with the age (P<.0001). In nursery piglets, treatment with ceftiofur had no influence on the occurrence of infections, fecal score (P>0.005), performance (P>0.005) and quantification of excreted fecal bacteria (P=0.6833). In conclusion, prophylactic use of ceftiofur on the first day of the piglets life was not able to reduce the occurrence of infections, had no influence in the frequency of days with altered fecal score and piglets did not excreted fewer bacteria in feces, however, piglets showed better performance during the suckling period, but not in the nursery period

A interação materno fetal na espécie equina depende exclusivamente da complexidade anatômica e fisiológica da placenta e este órgão endócrino provisório é a peça chave do presente estudo, onde objetivou-se avaliar a influência do número de partos sob a eficiência placentária. Buscando, por meio da morfometria das macro e microrregiões, além da expressão do VEGF, VEGFR-1/Flt-1 e VEGFR-2/FLK-1 na membrana corioalantóide a termo, dados referentes à inter-relação da pluriparidade, contato materno fetal e peso dos neonatos da raça Puro Sangue Inglês. O delineamento experimental consistiu em um estudo analítico, observacional, transversal, prospectivo. Foram acompanhados cinquenta partos de éguas divididas em três grupos de acordo com a pluriparidade: primíparas (n=18), 2 a 5 partos (n=14) e 6 a 10 partos (n=18). Foram coletados e fixados em formol fragmentos de 3 cm2 das regiões do corpo do útero (Cut), corno uterino gestante (CG) e corno uterino contralateral (CnG) da membrana corioalantóide a termo pós delivramento. Após processamento foram corados pela técnica de Hematoxilina & Eosina e Picro-Sirus-Red. Os estudos imunohistoquímico (método avidina-biotina) e esterológico foram realizados ao microscópio óptico. Foram correlacionados número de partos, altura e perímetro torácico (PT) maternos; idade, altura e PT paternos; composição volumétrica dos compartimentos placentários juntamente com as áreas de superfície de contato materno-fetal e peso, altura e escore de vitalidade neonatal. A paridade, além de diretamente relacionada ao peso do neonato, demonstrou na avaliação morfofuncional ser determinante ao ganho de eficiência placentária. As membranas corioalantóides das éguas pluríparas tenderam a apresentar maior volume total no CG, aumento na porcentagem e volume total de vilos, além de maior densidade microcotiledonária e expressão do VEGF na região do CG. Entre as muitas correlações determinadas no grupo primíparas as mais relevantes foram peso da membrana com variáveis neonatais como peso (r=0,598), PT (r=0,775), tempo para mamar (r=0,553) e tempo de gestação (r=-0,527), além do PT da mãe com o tempo para ruptura do cordão umbilical (r=0,564), reflexo de sucção (r=0,625), para levantar (r=0,756) e decúbito esternal (r=-590). Da mesma forma no grupo 2 a 5 partos, neonatos que nasceram com maior peso, altura, e PT apresentaram menor tempo para levantar (r=-0,546; r=-0,869, r=-0,892), eliminação do mecônio (r=-0,535) e ruptura do cordão umbilical (r=-0,528; r=-0,881). Assim como no grupo 6 a 10 partos, o peso do potro apresentou correlação com o peso (r=0,793), PT (r=0,716) e altura (r=0,667) materna. O volume total do CG correlacionou com volume total do parênquima (r=-0,816) e epitélio nos vilos placentários do CG (r=-0,915), tempo de gestação (r=-0,483), tempo para reflexo de sucção (r=-0,672), para mamar (r=-0,525), e para eliminação do mecônio (r=-0,525). No que diz respeito às variáveis paternas, o peso paterno correlacionou com o volume total do parênquima nos vilos placentários do CnG (r=0,393) , além do PT do garanhão com o peso (r=0,316) e PT (r=0,425) do potro e volume total do CG (r=0,319). Desta forma, acredita-se que estes resultados possam fornecer ferramentas práticas para auxiliar na escolha das fêmeas e machos mais indicados para geração de potros neonatos com desenvolvimento adequado. / Fetomaternal interaction in equine species depends exclusively on the complexity of placental anatomy and physiology. This transient endocrine organ is the key of the present study, which aimed to evaluate the influence of parity on placental efficiency. Morphometric of macro and micro regions, expression of VEGF, VEGFR-1/Flt-1 and VEGFR-2/FLK-1 in term corioallantois were performed and data regarding parity, fetomaternal contact and neonatal weight were evaluated in Thoroughbred. The experimental study consisted of an analytical, observational, cross-sectional, prospective study. Fifty deliveries were monitored in mares divided into three groups according to parity: nulliparous (n=18), 2 to 5 deliveries (n=14) and 6 to 10 deliveries (n=18). Tissue sections measuring 3 cm 2 were collected and fixed in formol saline from term chorioallantois regions: uterine body (UtB), pregnant uterine horn (PH) and contralateral uterine horn (CtH). After processing, samples were stained using Hematoxylineosin and Picro-Sirus-Red. Imunnohistochemistry (avidin-biotin method) and stereology were performed using an optic microscope. Correlations between parity, maternal height and thoracic perimeter; paternal age, height and thoracic perimeter; volume composition of placental compartments, surface area of fetomaternal contact and weight, height and neonatal vitality score were performed. Parity was directly related to weight of the neonate and demonstrated in morphofunctional evaluation to be determinant for placental efficiency. Chorioallantoic membranes from pluriparous mares tended to have greater total PH volume, higher percentage and total villi volume, and greater microcotiledonary density and VEGF expression in PH region. There were several correlations found in nulliparous group, the most relevant were membrane weight and neonatal parameters such as weight (r=0,598), thoracic perimeter (r=0,775), time to nurse (r=0,553) and gestational length (r=-0,527) and also mares thoracic perimeter with time to rupture the umbilical cord (r=0,564), suckle reflex (r=0,625), time to stand (r=0,756) and to achieve sternal recumbency (r=-590). Likewise, for the 2 to 5 deliveries group, neonates that were born heavier, taller and with greater thoracic perimeter took less time to stand (r=-0,546; r=-0,869, r=-0,892), pass meconium (r=-0,535) and rupture the umbilical cord (r=-0,528; r=-0,881). In the group of mares between 6 and 10 deliveries, foals weight was correlated to maternal weight (r=0,793), thoracic perimeter (r=0,716) and height (r=0,667). Total PH volume correlated to total parenchyma (r=-0,816) and epithelium in placental villi in PH (r=-0,915), gestational lenght (r=-0,483), time to suckle reflex (r=- 0,672), to nurse (r=-0,525), and pass meconium (r=-0,525). Regarding Paternal variables, paternal weight correlated to total parenchyma volume in placental villi of the CtH (r=0,393). Also thoracic perimeter of the stallion correlated to neonatal weight (r=0,316) thoracic perimeter (r=0,425) and total volume of the PH (r=0,319). Therefore, these data provides rationale for an adequate choice of mares and stallions to generate well-developed neonates.

A interação materno fetal na espécie equina depende exclusivamente da complexidade anatômica e fisiológica da placenta e este órgão endócrino provisório é a peça chave do presente estudo, onde objetivou-se avaliar a influência do número de partos sob a eficiência placentária. Buscando, por meio da morfometria das macro e microrregiões, além da expressão do VEGF, VEGFR-1/Flt-1 e VEGFR-2/FLK-1 na membrana corioalantóide a termo, dados referentes à inter-relação da pluriparidade, contato materno fetal e peso dos neonatos da raça Puro Sangue Inglês. O delineamento experimental consistiu em um estudo analítico, observacional, transversal, prospectivo. Foram acompanhados cinquenta partos de éguas divididas em três grupos de acordo com a pluriparidade: primíparas (n=18), 2 a 5 partos (n=14) e 6 a 10 partos (n=18). Foram coletados e fixados em formol fragmentos de 3 cm2 das regiões do corpo do útero (Cut), corno uterino gestante (CG) e corno uterino contralateral (CnG) da membrana corioalantóide a termo pós delivramento. Após processamento foram corados pela técnica de Hematoxilina & Eosina e Picro-Sirus-Red. Os estudos imunohistoquímico (método avidina-biotina) e esterológico foram realizados ao microscópio óptico. Foram correlacionados número de partos, altura e perímetro torácico (PT) maternos; idade, altura e PT paternos; composição volumétrica dos compartimentos placentários juntamente com as áreas de superfície de contato materno-fetal e peso, altura e escore de vitalidade neonatal. A paridade, além de diretamente relacionada ao peso do neonato, demonstrou na avaliação morfofuncional ser determinante ao ganho de eficiência placentária. As membranas corioalantóides das éguas pluríparas tenderam a apresentar maior volume total no CG, aumento na porcentagem e volume total de vilos, além de maior densidade microcotiledonária e expressão do VEGF na região do CG. Entre as muitas correlações determinadas no grupo primíparas as mais relevantes foram peso da membrana com variáveis neonatais como peso (r=0,598), PT (r=0,775), tempo para mamar (r=0,553) e tempo de gestação (r=-0,527), além do PT da mãe com o tempo para ruptura do cordão umbilical (r=0,564), reflexo de sucção (r=0,625), para levantar (r=0,756) e decúbito esternal (r=-590). Da mesma forma no grupo 2 a 5 partos, neonatos que nasceram com maior peso, altura, e PT apresentaram menor tempo para levantar (r=-0,546; r=-0,869, r=-0,892), eliminação do mecônio (r=-0,535) e ruptura do cordão umbilical (r=-0,528; r=-0,881). Assim como no grupo 6 a 10 partos, o peso do potro apresentou correlação com o peso (r=0,793), PT (r=0,716) e altura (r=0,667) materna. O volume total do CG correlacionou com volume total do parênquima (r=-0,816) e epitélio nos vilos placentários do CG (r=-0,915), tempo de gestação (r=-0,483), tempo para reflexo de sucção (r=-0,672), para mamar (r=-0,525), e para eliminação do mecônio (r=-0,525). No que diz respeito às variáveis paternas, o peso paterno correlacionou com o volume total do parênquima nos vilos placentários do CnG (r=0,393) , além do PT do garanhão com o peso (r=0,316) e PT (r=0,425) do potro e volume total do CG (r=0,319). Desta forma, acredita-se que estes resultados possam fornecer ferramentas práticas para auxiliar na escolha das fêmeas e machos mais indicados para geração de potros neonatos com desenvolvimento adequado. / Fetomaternal interaction in equine species depends exclusively on the complexity of placental anatomy and physiology. This transient endocrine organ is the key of the present study, which aimed to evaluate the influence of parity on placental efficiency. Morphometric of macro and micro regions, expression of VEGF, VEGFR-1/Flt-1 and VEGFR-2/FLK-1 in term corioallantois were performed and data regarding parity, fetomaternal contact and neonatal weight were evaluated in Thoroughbred. The experimental study consisted of an analytical, observational, cross-sectional, prospective study. Fifty deliveries were monitored in mares divided into three groups according to parity: nulliparous (n=18), 2 to 5 deliveries (n=14) and 6 to 10 deliveries (n=18). Tissue sections measuring 3 cm 2 were collected and fixed in formol saline from term chorioallantois regions: uterine body (UtB), pregnant uterine horn (PH) and contralateral uterine horn (CtH). After processing, samples were stained using Hematoxylineosin and Picro-Sirus-Red. Imunnohistochemistry (avidin-biotin method) and stereology were performed using an optic microscope. Correlations between parity, maternal height and thoracic perimeter; paternal age, height and thoracic perimeter; volume composition of placental compartments, surface area of fetomaternal contact and weight, height and neonatal vitality score were performed. Parity was directly related to weight of the neonate and demonstrated in morphofunctional evaluation to be determinant for placental efficiency. Chorioallantoic membranes from pluriparous mares tended to have greater total PH volume, higher percentage and total villi volume, and greater microcotiledonary density and VEGF expression in PH region. There were several correlations found in nulliparous group, the most relevant were membrane weight and neonatal parameters such as weight (r=0,598), thoracic perimeter (r=0,775), time to nurse (r=0,553) and gestational length (r=-0,527) and also mares thoracic perimeter with time to rupture the umbilical cord (r=0,564), suckle reflex (r=0,625), time to stand (r=0,756) and to achieve sternal recumbency (r=-590). Likewise, for the 2 to 5 deliveries group, neonates that were born heavier, taller and with greater thoracic perimeter took less time to stand (r=-0,546; r=-0,869, r=-0,892), pass meconium (r=-0,535) and rupture the umbilical cord (r=-0,528; r=-0,881). In the group of mares between 6 and 10 deliveries, foals weight was correlated to maternal weight (r=0,793), thoracic perimeter (r=0,716) and height (r=0,667). Total PH volume correlated to total parenchyma (r=-0,816) and epithelium in placental villi in PH (r=-0,915), gestational lenght (r=-0,483), time to suckle reflex (r=- 0,672), to nurse (r=-0,525), and pass meconium (r=-0,525). Regarding Paternal variables, paternal weight correlated to total parenchyma volume in placental villi of the CtH (r=0,393). Also thoracic perimeter of the stallion correlated to neonatal weight (r=0,316) thoracic perimeter (r=0,425) and total volume of the PH (r=0,319). Therefore, these data provides rationale for an adequate choice of mares and stallions to generate well-developed neonates.