Mother’s milk contains complex microbial communities thought to be important for colonizing a preterm infant’s gastrointestinal tract. However, little is known about the microbiota in the preterm mother’s milk and factors influencing its composition. We characterized the temporal dynamics of microbial communities in 490 breast milk samples from 86 mothers of preterm infants (born <1,250g) over the first 8 weeks postpartum. Highly individualized microbial communities were identified in each mother’s milk that changed temporally with notable alterations in predicted microbial functions. However, pre-pregnancy BMI, delivery mode, and antibiotics were associated with changes in these microbial dynamics. Individual classes of antibiotics and their duration of exposure during prenatal and postpartum periods showed unique relationships with microbial taxa abundance and diversity in mother’s milk. These results highlight the temporal complexity of the preterm mother’s milk microbiota and its relationship with maternal characteristics as well as the importance of discussing antibiotic stewardship for mothers.

母乳中含有复杂的微生物群落，这些微生物群对于定居早产儿的胃肠道至关重要。但是，对于早产母乳中的微生物群及其影响因素知之甚少。我们表征了来自产后前8周的86个早产母亲（出生于<1,250g）母亲的490个母乳样品中微生物群落的时间动态。在每个母乳中鉴定出高度个体化的微生物群落，这些微生物随预测的微生物功能的显着变化随时间变化。但是，孕前的BMI，分娩方式和抗生素与这些微生物动力学的变化有关。产前和产后各个类别的抗生素及其接触时间显示出与母乳中微生物分类单元的丰富性和多样性的独特关系。这些结果突出了早产母亲的牛奶菌群的时间复杂性及其与母亲特征的关系，以及讨论母亲的抗生素管理工作的重要性。