Mode of delivery affects perinatal lung liquid changes and clinical adaptation of the newborn
Creators: name: Pfister, Riccardo
Publisher: name: Université de Genève
Year: 2010
Subjects: info:eu-repo/classification/ddc/618
Caesarean section
Neonate
Fetus
Lung liquid
Labour

description: Introduction: Caesarean section (CS) rates are increasing worldwide and pre-labour CS do so at the highest rate. Although CS undoubtedly save some lives, it is equally true that higher neonatal mortality and morbidities, particularly in relation to lung adaptation at birth, are associated with this mode of delivery. Despite recognition that clearance of the liquid filling the fetal lung is an essential step in the establishment of effective postnatal air-breathing, the pathophysiologic mechanisms of neonatal respiratory morbidity after CS are still under debate. We therefore lack insight for development of novel approaches to improve respiratory outcome in the newborn infant, the primary neonatal pathology. Objective: To summarises up-to-date clinical and animal research providing insight into the effect of delivery mode on lung liquid clearance and on respiratory adaptation at birth. Method: A non-systematic translational pathophysiologic review based on the last 30 years of experimental data to corroborate clinical epidemiological findings. Review: The bulk of research in perinatal lung adaptation and respiratory distress at birth has focused on surfactant. Little translational research has put lung liquid clearance into clinical context, yet it is known that infants delivered by CS have more liquid left in the airspaces of their lungs compared to infants born vaginally at a similar gestational age. Both, the regulation of lung volume during gestation, and the influence of labour and mode of delivery on perinatal clearance of lung liquid, have a major impact on how the lung becomes adapted for birth. Transformation of the lung, from its fetal state of liquid secretion to its neonatal mode, when it is in essence a dry organ of air breathing, is crucial for gas exchange. The importance of this change, on which all organs count for vital oxygenation, depends on several distinct but connected physiological changes that are linked to labour. The review will provide explanations for diverging results in the past and consider the timing of lung liquid clearance via the two available pathways, one across the alveolar epithelium, the other through the airways. As a final goal, the review will provide clinicians involved with perinatal issues with up-to-date understanding of the physiology of fetal lung liquid clearance and how lack of labour through CS delivery affects neonatal lung adaptation at birth. Conclusion: Clinical and experimental evidence suggests that pre-labour birth not only results in relative prematurity, but additionally curtails the extent of lung liquid clearance that occurs in a normal vaginal delivery at term. Although steroids can be used to improve maturation of the pulmonary gas exchange ‘machinery', the active expulsion of lung liquid via the airways appears to relate to the occurrence of uterine contractions, while the normal trigger for trans-epithelial liquid absorption in the ante- and post-natal lung depends on a labour-induced adrenaline surge.