Data for: The relationship between neutrophil-lymphocyte ratio and onset of lactation among postpartum women: A prospective observational cohort study
Background: Delayed onset of lactation is a key factor in the low rate of exclusive breast-feeding in 6 months after caesarean section. The mechanism of delayed onset of lactation is not clear. Milk production depends largely on mitochondrial adenosine triphosphate synthesis, and the neutrophil-lymphocyte ratio is closely related to mitochondrial deoxyribonucleic acid copy number and adenosine triphosphate production. Presently, it is unclear whether a difference in the neutrophil-lymphocyte ratio exists between those undergoing vaginal delivery and those undergoing caesarean delivery and, if so, whether the difference correlates to the time of onset of lactation. Objectives: To identify whether the neutrophil-lymphocyte ratio at 24 hours after delivery is different between mothers delivering by caesarean section and those giving birth vaginally and whether the neutrophil-lymphocyte ratio is related to the delayed onset of lactation. Design: The study adopted a prospective cohort study design. Settings: Maternity units of an Obstetrics & Gynecology Hospital. Participants: 327 mother-infant pairs who met inclusion/exclusion criteria and were followed up to the time of onset of lactation. Methods: Mother-infant pairs were allocated to the vaginal birth group or the caesarean section group according to birth method. The neutrophil-lymphocyte ratio was calculated as the absolute value of neutrophils divided by the absolute value of lymphocytes based on full blood counts. Before delivery, full blood counts were obtained from medical records. After delivery, blood samples were drawn 24 hours postpartum, and blood cells were classified and counted. The onset of lactation was confirmed by the maternal perception of breast fullness. The neutrophil-lymphocyte ratio and its relationship with lactation onset were analyzed by multivariable regression. Results: The neutrophil-lymphocyte ratios of both groups were elevated after delivery. Based on the covariance analysis, after adjusting for baseline full blood counts before delivery, the neutrophil-lymphocyte ratio in the caesarean group was higher than the ratio in the vaginal group after delivery (p = .000). In addition, after adjustment for confounding factors, multivariable regression analyses showed that an increased neutrophil-lymphocyte ratio was correlated with delayed onset of lactation (95% confidence interval 0.285-1.646). Conclusions: The neutrophil-lymphocyte ratio in the caesarean section group was higher than that in the vaginal delivery group and was related to a delayed onset of lactation. Given the decreased mitochondrial copy number in the elevated neutrophil-lymphocyte ratio and therefore the associated reduction in adenosine triphosphate synthesis, these findings may elucidate the mechanism for delayed onset of lactation in caesarean section births.