This study aimed to assess global trends in mean birthweights at term, as reported in peer-reviewed literature. We electronically searched PubMed, Embase, and Web of Science up to September 2023, using combinations of the search terms: “birth weight”; “birth-weight”; “birthweight”; “trend”. There were no restrictions based on language or geographic area. We included all ecological and observational studies reporting mean birthweight at term as a continuous numerical variable over time. We assessed the quality of included studies using the Dufault and Klar checklist modified by Betran et al. Univariate and multivariate linear models were used to examine the effects of time (years) and geographical origins. Subgroup analyses focused on national data sources and on data collected from 1950 onward. Among 6447 reviewed articles, 29 met our criteria, reporting mean birthweight data from over 183 million infants worldwide. Most studies were hospital-based (48.3%), 44.8% used national data, and a minority used municipality, community, or regional data (6.9%). Geographically, North America (31.0%) had the highest representation, followed by Asia and Europe (27.6% each), and South America and Oceania (6.9% each). Our univariate linear regression model (Model 1) revealed a significant increase in mean birthweight at term over time (4.74 g/y; 95% confidence interval, 3.95–5.53; <.001). Model 2, incorporating continental dummy variables into the first model, confirmed this trend (3.85 g/y; 95% confidence interval, 2.96–4.74; <.001). Model 3, focusing on available national data, did not find a significant relationship. Model 4 narrowed its focus on records from 1950 onward, reporting a robust annual increase of 7.26 g/y (95% confidence interval, 6.19–8.33; <.001). Model 5, adjusting for the number of participants included in each study, reported a conclusive mean term birthweight increase of 1.46 g/y (95% confidence interval, 0.74–2.18; <.001). This systematic review of 29 studies shows an increase in term birthweights over time, particularly when considering data since 1950. Limitations include study quality variations, data source diversity, and data sparsity, underscoring the need for future research to use precise gestational age distinctions and predetermined time frames to gain a deeper understanding of this trend and its implications for maternal and child health.

中文翻译：

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全球足月出生体重有所增加：对 1.83 亿新生儿进行系统回顾的见解

本研究旨在评估同行评审文献中报道的足月平均出生体重的全球趋势。我们使用以下搜索词组合对 PubMed、Embase 和 Web of Science 进行了截至 2023 年 9 月的电子搜索：“出生体重”； “出生体重”; “出生体重”; “趋势”。没有语言或地理区域的限制。我们纳入了所有将足月平均出生体重报告为随时间变化的连续数值变量的生态和观察研究。我们使用 Betran 等人修改的 Dufault 和 Klar 检查表评估了纳入研究的质量。使用单变量和多元线性模型来检验时间（年）和地理起源的影响。亚组分析侧重于国家数据源和 1950 年以来收集的数据。在 6447 篇已审阅的文章中，有 29 篇符合我们的标准，报告了全球超过 1.83 亿婴儿的平均出生体重数据。大多数研究以医院为基础（48.3%），44.8% 使用国家数据，少数研究使用市、社区或地区数据（6.9%）。从地域上看，北美洲（31.0%）的代表性最高，其次是亚洲和欧洲（各 27.6%）、南美洲和大洋洲（各 6.9%）。我们的单变量线性回归模型（模型 1）显示，随着时间的推移，足月平均出生体重显着增加（4.74 克/年；95% 置信区间，3.95–5.53；<.001）。模型 2 将大陆虚拟变量纳入第一个模型，证实了这一趋势（3.85 g/y；95% 置信区间，2.96–4.74；<.001）。模型 3 侧重于现有的国家数据，没有发现显着的关系。从 1950 年起，模型 4 缩小了对记录的关注范围，报告每年强劲增长 7.26 克/年（95% 置信区间，6.19–8.33；<.001）。模型 5 根据每项研究中的参与者数量进行调整，得出结论性平均足月出生体重增加 1.46 克/年（95% 置信区间，0.74–2.18；<.001）。对 29 项研究的系统回顾显示，足月出生体重随着时间的推移而增加，特别是考虑到 1950 年以来的数据时。局限性包括研究质量差异、数据源多样性和数据稀疏性，强调未来的研究需要使用精确的胎龄差异和预先确定的数据。更深入地了解这一趋势及其对孕产妇和儿童健康的影响的时间框架。