Birth weight is closely related to individual health. Low birth weight is a high-risk factor for early neonatal death. Macrosomia is associated with higher risk of maternal and infant complications and various chronic diseases in adulthood. Therefore, it is very important to identify the influencing factors of neonatal birth weight.

To investigate the relationship between maternal intestinal flora and neonatal birth weight.

Participants were 516 singleton mothers and their babies〔24 with low birth weight (LW group) , 479 with normal birth weight (NW group) and 13 with macrosomia (OW group) 〕 delivered at term in Guangzhou Women and Children's Medical Center from January to September 2017. Maternal intestinal flora and clinical laboratory test parameters were collected, and the composition and diversity of intestinal flora were analyzed using QIIME. LEfSe analysis was used to compare the relative abundance of intestinal flora at the genus level of the mothers of three groups of babies to identify the flora with significant intergroup differences. MaAslin was used to assess associations of maternal laboratory test parameters and microbial genera. The Boruta was used to build models for predicting three types of neonatal birth weight using maternal laboratory test parameters and intestinal flora OTUs, to assess the association of maternal intestinal floras and neonatal birth weight.

The analysis of maternal intestinal floras showed that the abundance of Firmicutes was the highest at the phylum level, and Faecalibacterium was significantly enriched at the genus level. There were no significant differences in Simpson's Diversity Index and Shannon Diversity Index at the phylum level across the maternal intestinal floras of three groups of babies (P>0.05) . LEfSe analysis found that compared with intestinal flora of mothers of LW group, the intestinal flora of mothers of NW group showed significantly enriched Streptococcus and Roseburia (P<0.05) , and significantly reduced abundance of Bacillaceae, Raphanus, Methanosphaera, Barnesiella and Paraprevotella (P<0.05) , while the intestinal flora of mothers of OW group demonstrated significantly enriched Closrtidiaceae and Alistipes as well as significantly reduced abundance of Barnesiella (P<0.05) . Compared with intestinal flora of mothers of NW group, the intestinal flora of mothers of OW group indicated significantly enriched Megamonas, Coprococcus, Veillonellaceae, cc-115, Closrtidiaceae and Alistipes, and significantly reduced abundance of Blautia and Eggerthella (P<0.05) . The area under ROC curve (AUC value) based on laboratory test parameter OTUs model and intestinal flora OTUs model was 0.62 and 0.77, respectively, in discriminating LW from NW, and was 0.65, and 0.78 respectively, in discriminating OW from NW.

Neonatal birth weight varied by the features of maternal intestinal floras. The OTUs model based on maternal intestinal flora could distinguish the neonatal birth weight. Maternal intestinal flora may be a good predictor of neonatal birth weight.

新生儿出生体质量与个体健康息息相关，低出生体质量是早期新生儿死亡的高危因素，而巨大儿的发生不仅可增加母婴产时并发症发生风险，还可增加个体成年后罹患各种慢性病的风险。因此，寻找新生儿出生体质量的影响因素十分重要。

探讨孕妇肠道菌群对新生儿出生体质量的影响。

以2017年1—9月在广州市妇女儿童医疗中心出生的516例新生儿及其孕母为研究对象，根据新生儿出生体质量将其分为低出生体质量儿组（LW组，n=24）、正常体质量儿组（NW组，n=479）、巨大儿组（OW组，n=13）。采集孕母的肠道菌群参数及临床实验室检测指标，采用QIIME软件进行孕期肠道菌群组成分析和多样性分析；采用LEfSe分析，分别对三组孕妇肠道菌群属水平上的相对丰度进行两两比较，识别组间具有明显差异的菌群；通过线性模型MaAsLin进行多元分析，以捕获各实验室检测指标与微生物属之间的相关性；通过Boruta随机森林分类器模型分别基于实验室检测指标和肠道菌群分类操作单元（OTUs）构建新生儿出生体质量分类预测模型，探究孕妇肠道菌群对新生儿体质量的影响。

三组孕母的肠道菌群组成分析发现，门水平中厚壁菌门（Firmicutes）物种丰富度最高，属水平里普拉梭菌（Faecalibacterium）明显富集，三组间门水平的香农指数和辛普森指数比较，差异无统计学意义（P>0.05）。三组间的LEfSe分析发现：与LW组比较，NW组链球菌（Streptococcus）和罗氏菌（Roseburia）明显富集（P<0.05），而芽孢杆菌（Bacillaceae）、萝卜属菌（Raphanus）、甲烷球形菌（Methanosphaera）、巴氏杆菌（Barnesiellaceae）、普雷沃氏菌（Paraprevotella）丰度明显降低（P<0.05）；与NW组比较，OW组属巨单胞菌（Megamonas）、属粪球菌（Coprococcus）、韦荣氏菌（Veillonellaceae）、cc-115、梭菌（Closrtidiaceae）、另枝杆菌（Alistipes）明显富集（P<0.05），而布劳特氏菌（Blautia）和伊格尔兹氏菌（Eggerthella）丰度明显降低（P<0.05）；与LW组比较，OW组Closrtidiaceae、Alistipes菌群明显富集（P<0.05），而Barnesiellaceae丰度明显降低（P<0.05）。基于实验室检测指标分类器模型、肠道菌群OTUs分类器模型，区分NW组与LW组的受试者工作特征曲线下面积（AUC）分别为0.62、0.77，区分NW组与OW组的AUC分别为0.65、0.78。

不同出生体质量新生儿对应孕母的肠道菌群存在差异，孕母肠道菌群OTUs模型可区分新生儿出生体质量的大小，孕妇肠道菌群可能是预测新生儿体质量的一个良好指标。