Abstract: Background　Delayed onset of lactogenesis Ⅱ（DOLⅡ） has been proven to increase the rate of early breastfeeding cessation and shorten the duration of breastfeeding as well as raise the risk of excessive weight loss and formula milk supplementation among newborns. Therefore，understanding the incidence and influencing factors of DOLⅡ，and formulating effective interventions have a positive impact on breastfeeding. Objective　To systematically evaluate the incidence and influencing factors of DOLⅡ，to provide a scientific basis for conducting relevant research and delivering targeted interventions. Methods　Web of Science，PubMed，EMBase，Cochrane Library，VIP，CNKI，Wanfang Data and CBM were searched to collect literature about the incidence and influencing factors of DOLⅡ. Data extraction and methodological quality evaluation were performed by two researchers separately. Meta-analysis of quantitative data was conducted using Stata 12.0 software. Results　A total of 26 studies were included，and 25 of which had a report of DOLⅡincidence of 26%〔95%CI（21%，30%）〕. Meta-analysis showed that primiparity，cesarean section，gestational diabetes mellitus，insulin injection，pre-pregnancy BMI-based overweight or obesity，anxiety，depression，and delayed breastfeeding initiation time were risk factors of DOLⅡ （P<0.05），while maternal age and neonatal birth weight>3 600 g were not significantly associated with DOLⅡ （P>0.05）. Conclusion　The incidence of DOLⅡ is relatively high，which is associated with primiparity，cesarean section，gestational diabetes mellitus，insulin injection，pre-pregnancy BMI-based overweight or obesity，anxiety，depression，and delayed breastfeeding initiation time. There are still different opinions on the role of some risk factors in the development of DOLⅡ，and the causal relationship of them with DOLⅡ needs to be further verified.

Key words: Breast feeding, Prolonged lactations, LactogenesisⅡ, Root cause analysis, Meta-analysis, Systematic review

摘要： 背景　产后泌乳Ⅱ期启动延迟（DOLⅡ）被证实可提高早期母乳喂养停止率和缩短母乳喂养持续时间，增加新生儿体质量过多减轻及配方奶粉补充的风险。因而，了解DOLⅡ发生现状、甄别DOLⅡ的影响因素、制定有效的干预措施对于母乳喂养具有积极影响。目的　系统评价DOLⅡ的发生率及影响因素，为相关研究和干预提供借鉴。方法　计算机检索Web of Science、PubMed、EMBase、Cochrane Library、维普网、中国知网、万方数据知识服务平台和中国生物医学文献数据库中关于DOLⅡ发生率及影响因素的文献；两名研究者对文献进行质量评价和资料提取、系统评价；符合量性分析的资料使用Stata 12.0软件行Meta分析。结果　共纳入26篇文献进行系统评价，基于25篇文献的Meta分析结果显示，DOLⅡ发生率为26%〔95%CI（21%，30%）〕。Meta分析结果显示，初产、剖宫产、妊娠期糖尿病、注射胰岛素、孕前超重或肥胖、焦虑、抑郁、开奶时间晚是DOLⅡ的危险因素（P<0.05）；年龄、新生儿出生体质量>3 600 g对DOLⅡ的影响无统计学意义（P>0.05）。结论　DOLⅡ发生率较高，初产、剖宫产、妊娠期糖尿病、注射胰岛素、孕前超重或肥胖、焦虑、抑郁、开奶时间晚是DOLⅡ的危险因素，但部分因素的作用仍有不同评价，与DOLⅡ的因果关系有待进一步验证。

关键词: 母乳喂养, 延长泌乳, 泌乳Ⅱ期, 影响因素分析, Meta分析, 系统评价