Background

Intrauterine and postnatal weight are widely regarded as biomarkers of fetal and neonatal wellbeing, but optimal weight gain following preterm birth is unknown. We aimed to describe changes over time in birthweight and postnatal weight gain in very and extremely preterm babies, in relation to major morbidity and healthy survival.

Methods

In this cohort study, we used whole-population data from the UK National Neonatal Research Database for infants below 32 weeks gestation admitted to neonatal units in England and Wales between Jan 1, 2008, and Dec 31, 2019. We used non-linear Gaussian process to estimate monthly trends, and Bayesian multilevel regression to estimate unadjusted and adjusted coefficients. We evaluated birthweight; weight change from birth to 14 days; weight at 36 weeks postmenstrual age; associated Z scores; and longitudinal weights for babies surviving to 36 weeks postmenstrual age with and without major morbidities. We adjusted birthweight for antenatal, perinatal, and demographic variables. We additionally adjusted change in weight at 14 days and weight at 36 weeks postmenstrual age, and their Z scores, for postnatal variables.

Findings

The cohort comprised 90 817 infants. Over the 12-year period, mean differences adjusted for antenatal, perinatal, demographic, and postnatal variables were 0 g (95% compatibility interval −7 to 7) for birthweight (−0·01 [–0·05 to 0·03] for change in associated Z score); 39 g (26 to 51) for change in weight from birth to 14 days (0·14 [0·08 to 0·19] for change in associated Z score); and 105 g (81 to 128) for weight at 36 weeks postmenstrual age (0·27 [0·21 to 0·33] for change in associated Z score). Greater weight at 36 weeks postmenstrual age was robust to additional adjustment for enteral nutritional intake. In babies surviving without major morbidity, weight velocity in all gestational age groups stabilised at around 34 weeks postmenstrual age at 16–25 g per day along parallel percentile lines.

Interpretation

The birthweight of very and extremely preterm babies has remained stable over 12 years. Early postnatal weight loss has decreased, and subsequent weight gain has increased, but weight at 36 weeks postmenstrual age is consistently below birth percentile. In babies without major morbidity, weight velocity follows a consistent trajectory, offering opportunity to construct novel preterm growth curves despite lack of knowledge of optimal postnatal weight gain.

Funding

UK Medical Research Council.

中文翻译：

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2008-19 年英格兰和威尔士极早产儿和极早产儿的出生体重和产后体重增加模式：一项队列研究

背景

宫内和产后体重被广泛认为是胎儿和新生儿健康的生物标志物，但早产后的最佳体重增加尚不清楚。我们旨在描述极早产儿和极早产儿的出生体重和产后体重随时间的变化与主要发病率和健康生存率的关系。

方法

在这项队列研究中，我们使用了来自英国国家新生儿研究数据库的全人群数据，用于 2008 年 1 月 1 日至 2019 年 12 月 31 日期间在英格兰和威尔士的新生儿病房入住的孕 32 周以下婴儿。我们使用非线性高斯估计每月趋势的过程，以及估计未调整和调整系数的贝叶斯多级回归。我们评估了出生体重；从出生到 14 天的体重变化；月经后 36 周时的体重；相关的 Z 分数；存活至月经后 36 周的婴儿的纵向体重和纵向体重，无论有无重大疾病。我们根据产前、围产期和人口统计学变量调整了出生体重。我们还针对产后变量调整了 14 天时的体重变化和 36 周时的体重变化，以及它们的 Z 分数。

发现

该队列包括 90 817 名婴儿。在 12 年期间，针对出生体重（-0·01 [–0·05 至 0·03]相关 Z 分数的变化）；从出生到 14 天体重变化为 39 g（26 至 51）（相关 Z 评分变化为 0·14 [0·08 至 0·19]）；和 105 g (81 到 128) 用于月经后 36 周时的体重（0·27 [0·21 到 0·33] 相关 Z 分数的变化）。经后 36 周体重增加对肠内营养摄入的额外调整是稳健的。在没有发生重大疾病的情况下存活的婴儿中，所有孕龄组的体重速度在月经后 34 周左右沿平行百分位线稳定在每天 16-25 克。

解释

12 年来，极早产和极早产婴儿的出生体重一直保持稳定。产后早期体重减轻减少，随后体重增加增加，但月经后 36 周时的体重始终低于出生百分位数。在没有重大发病率的婴儿中，体重速度遵循一致的轨迹，尽管缺乏最佳产后体重增加的知识，但提供了构建新的早产生长曲线的机会。

资金

英国医学研究委员会。