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.

研究背景：剖宫产术后6个月内纯母乳喂养率偏低的关键诱因之一为泌乳启动延迟。目前泌乳启动延迟的具体发病机制尚未明确。乳汁生成在很大程度上依赖线粒体三磷酸腺苷（adenosine triphosphate, ATP）的合成，而中性粒细胞与淋巴细胞比值（neutrophil-lymphocyte ratio, NLR）与线粒体脱氧核糖核酸（mitochondrial deoxyribonucleic acid, mtDNA）拷贝数及ATP生成水平密切相关。目前尚不清楚阴道分娩与剖宫产产妇的NLR是否存在差异，若存在差异，该差异是否与泌乳启动时间相关。
研究目的：明确剖宫产与阴道分娩产妇在分娩后24小时的中性粒细胞与淋巴细胞比值是否存在差异，并探究该比值与泌乳启动延迟的相关性。
研究设计：本研究采用前瞻性队列研究设计。
研究地点：某妇产科医院产科病房。
研究对象：符合纳入/排除标准的327对母婴对，所有研究对象均被随访至泌乳启动时刻。
研究方法：根据分娩方式将研究对象分为阴道分娩组与剖宫产组。基于全血细胞计数结果，以中性粒细胞绝对数与淋巴细胞绝对数的比值计算中性粒细胞与淋巴细胞比值。分娩前的全血细胞计数数据取自病历资料。分娩后24小时采集外周血样本，进行血细胞分类计数。通过产妇自我报告的乳房充盈感确认泌乳启动时间。采用多变量回归分析中性粒细胞与淋巴细胞比值及其与泌乳启动时间的相关性。
研究结果：两组产妇分娩后的中性粒细胞与淋巴细胞比值均较基线升高。经协方差分析校正分娩前基线全血细胞计数参数后，剖宫产组产妇分娩后的NLR显著高于阴道分娩组（p=0.000）。此外，在校正混杂因素后，多变量回归分析结果显示，中性粒细胞与淋巴细胞比值升高与泌乳启动延迟呈显著相关（95%置信区间：0.285~1.646）。
研究结论：剖宫产组产妇的中性粒细胞与淋巴细胞比值高于阴道分娩组，且该比值与泌乳启动延迟相关。鉴于NLR升高伴随线粒体拷贝数降低，进而导致ATP合成减少，本研究结果或可阐明剖宫产产妇泌乳启动延迟的潜在发病机制。