Am J Epidemiol. 2014 Jun 1;179(11):1366-74. doi: 10.1093/aje/kwu062. Epub 2014 May 2.
The initial Vanguard Study of the National Children's Study was conducted during 2009-2010 in 7 locations in the United States. A goal was to evaluate the feasibility and yield of a household-based sampling design to recruit pregnant women. A multistage area probability sampling design was used to identify study locations (generally, counties) that were subsequently divided into smaller geographical units, termed segments. Between 7 and 18 segments were selected in each location, and dwelling units within segments were listed. A household-based recruitment process was implemented, which included enumeration of households to identify age-eligible women, pregnancy screening to identify pregnant women eligible for immediate enrollment and nonpregnant women for telephone follow-up, and administration of informed consent to eligible women. After a recruitment period of 17-20 months, 67,181 (89%) households were enumerated, which identified 34,172 (88%) age-eligible women to whom the pregnancy screener was administered. Among those who completed the screener, 2,285 women became eligible for enrollment, of whom 1,399 (61%) enrolled. Although response rates were fairly high at initial contact and among pregnant women, the overall yield was lower than anticipated. In particular, telephone follow-up of nonpregnant women was not a practicable strategy for prospective recruitment of newly pregnant women.
初始 Vanguard国家儿童研究是在 2009 年至 2010 年期间在美国的 7 个地点进行的。其目的是评估基于家庭的抽样设计招募孕妇的可行性和效果。采用多阶段区域概率抽样设计来确定研究地点（通常为县），然后将这些地点进一步划分为较小的地理单元，称为段。每个地点选择 7 到 18 个段，然后列出段内的住宅单元。实施了基于家庭的招募流程，包括对家庭进行普查以确定符合年龄要求的妇女、对符合立即入组条件的孕妇进行妊娠筛查以及对不符合条件的孕妇进行电话随访，并向符合条件的妇女告知知情同意书。在 17-20 个月的招募期后，共普查了 67,181 户（89%），确定了 34,172 名（88%）符合年龄要求的妇女，对其进行了妊娠筛查。在完成筛查的妇女中，有 2,285 名妇女符合入组条件，其中 1,399 名（61%）入组。尽管初始接触和孕妇的反应率相当高，但总体效果低于预期。特别是，对未怀孕妇女的电话随访对于潜在招募新孕妇来说并不是一种可行的策略。
