Savitz David A
Department of Community and Preventive Medicine, Mount Sinai School of Medicine, One Gustave L. Levy Place, Box 1057, New York, NY 10029, USA.
Am J Epidemiol. 2008 Nov 1;168(9):990-2; discussion 993-4. doi: 10.1093/aje/kwn193. Epub 2008 Aug 27.
Identifying the causes of preterm birth has been problematic, in part because of heterogeneous pathways leading to the same event, early delivery. If a risk factor affects only a subset of cases, then studies that address the aggregate outcome will generate diluted measures of association. McElrath et al. (Am J Epidemiol. 2008;168(9):980-989) examined an array of potential influences on very early preterm birth (<28 weeks' gestation) and divided cases on the basis of proximal causes. Through factor analysis, they found empirical support for dividing preterm cases into 2 groups: intrauterine inflammation (preterm labor, preterm membrane rupture, placental abruption, and cervical insufficiency) and abnormal placentation (preeclampsia and intrauterine growth restriction). Replication of this classification in less extreme preterm births is needed, requiring large numbers of preterm births that have been characterized in detail. Nonetheless, this division is worthy of study by using previously collected data to determine whether, in fact, stronger associations are found for these subsets than for preterm birth in the aggregate. Ultimately, the test of the approach is in improving our understanding of etiology, ideally generating stronger, more consistent associations with preterm birth subsets than have been found for preterm birth in the aggregate.
确定早产原因一直存在问题，部分原因是导致早产这一相同事件的途径具有异质性。如果一个风险因素仅影响部分病例，那么针对总体结果的研究将产生稀释的关联度量。麦克尔拉思等人（《美国流行病学杂志》。2008年；168(9):980 - 989）研究了一系列对极早早产（妊娠<28周）的潜在影响，并根据近端原因对病例进行了分类。通过因子分析，他们发现了将早产病例分为两组的实证依据：宫内炎症（早产、胎膜早破、胎盘早剥和宫颈机能不全）和胎盘异常（子痫前期和胎儿生长受限）。需要在不太极端的早产中重复这种分类，这需要大量已详细特征化的早产病例。尽管如此，利用先前收集的数据来确定事实上这些亚组是否比总体早产有更强的关联，这种划分值得研究。最终，该方法的检验在于增进我们对病因的理解，理想情况下，与早产亚组产生比总体早产更强、更一致的关联。
