Docosahexaenoic acid (DHA) is a good source of fat that can be taken up through food, such as fish, or taken as a supplement. Evidence is building that DHA provides a high-yield, low-risk strategy to reduce preterm birth and/or low birth weight. These births are great costs to society. A recently completed Phase III trial revealed that higher birth weight and gestational age were associated with DHA dosed at 600 mg/day. In this article, we take a posterior predictive approach to assess impacts of these findings on public health. Simple statistical models are not adequate for accurate posterior predictive distribution estimation. Of particular interest is that the joint distribution of birth weight and gestational age is well modeled by a finite mixture of three normal distributions. Data from our own clinical trial exhibit similar features. Using the mean and variance-covariance matrices from a previous study and flexible commensurate priors for the mixing parameters, we estimate the effect of DHA supplementation on over 20,000 infants born in hospitals demographically similar to the hospital where the clinical trial was conducted.

二十二碳六烯酸（DHA）是脂肪的良好来源，可以通过食物（例如鱼）摄取或作为补充摄取。越来越多的证据表明，DHA提供了高产，低风险的策略来减少早产和/或低出生体重。这些出生对社会造成了巨大的损失。最近完成的一项III期临床试验表明，DHA剂量为600 mg /天与较高的出生体重和胎龄有关。在本文中，我们采用后验预测方法来评估这些发现对公共卫生的影响。简单的统计模型不足以进行准确的后验预测分布估计。特别令人感兴趣的是，通过三个正态分布的有限混合很好地模拟了出生体重和胎龄的联合分布。我们自己的临床试验数据显示出相似的特征。