The Immunological Effects of Caesarean Sections on Newborns in São Paulo, Brazil

Abstract

Background: In 1985, the World Health Organization stated: “There is no justification for any region to have Caesarean section rates higher than 10-15%.” Since this recommendation, several studies have shown an inverse association between national Caesarean section rates and maternal and infant morbidity and mortality at a population level, particularly in lower income countries with limited access to obstetric and neonatal care. Further studies have also demonstrated poor outcomes in children born by Caesarean section with the development of chronic respiratory problems and diabetes. As a case study, Brazil has one of the highest rates of Caesarean deliveries in the world, with some private hospitals exclusively performing this procedure, many of which are elective without medical indication. To analyze the immediate effects of Caesarean section on neonatal immunology, the medical records of two groups of newborns born via different delivery methods in the same hospital in São Paulo, Brazil were investigated.

Design: Retrospective cohort study, using existing databases of medical records.

Methods: The hemogram results of newborns delivered by either Caesarean section (n=368) or normal vaginal birth (n=283) between October 2005 and June 2015 were collected from the Children’s Institute (Instituto da Criança) of the University of São Paulo Faculty of Medicine Clinics Hospital (HCFMUSP). Neonatal hemogram results, such as leukocyte and neutrophil counts, were then analyzed against variables such as mode of delivery, complications during labor, and measurements at birth (e.g. gestational age, weight at birth, approximated month of conception). The Mann-Whitney-Wilcoxon test and the Fisher-Pitman Permutation test were used to test significance.

Results: We found statistically significant correlations between mode of delivery and red cell distribution width, leukocytes, precursor granulocytes, neutrophils and eosinophils; birth weight and Caesarean sections; gestational age and Caesarean sections; and birth weight and gestational age.

Conclusion: Caesarean section births were significantly negatively correlated with the following hemogram variables: erythrocytes, hematocrit counts, leukocytes, band neutrophils, segmented neutrophils, neutrophils and platelets. Caesarean section newborns were more likely to be conceived earlier in the year, with higher counts in the months before São Paulo’s seasonal influenza peak. Birth weight and gestational age are positively correlated.

Discussion: Caesarean sections negatively affect the immunological profile of neonates compared to normal vaginal birth, as the latter can confer immune benefits such as gut microbacteria, antibody transfer and stress hormone activation.

Keywords: Caesarean sections, vaginal delivery, birth weight, gestational age, leukocytes, neutrophils