Trends in C-Section and Induction Use among US Births and Consequences for US Birth Weight

项目摘要 美国的平均出生体重在20世纪90年代和21世纪初大幅下降，但并没有 恢复到下降前的出生体重水平。该项目记录了各州出生体重的趋势。 在1990至1990年间由非西班牙裔黑人、非西班牙裔白人和拉丁裔妇女所生的美国婴儿中 2014年。该项目调查了剖宫产率(剖腹产率)增加的程度 而引产是美国出生体重最近发生变化的原因。到目前为止，现有的研究已经 报告称，美国出生体重下降与剖腹产使用率增加之间没有联系 引诱。此外，现有证据表明，美国出生体重分布已经发生了变化 在孕期的所有周。因此，美国出生体重的异常下降被怀疑是 反映与胎龄无关的胎儿生长减少的来源。然而，分析 现有研究的方法忽略了胎龄出生的构成如何 由于剖腹产和引产的使用增加而发生变化。更多地使用剖腹产和引产 并不是随机的。相反，它们不成比例地发生在选定的孕龄，这已经 美国出生的时间和方式发生了戏剧性的变化。这些分娩干预措施通常会影响怀孕。 这很可能会导致较高的胎龄和较高的出生体重，如果 干预措施没有发生。这些变化的后果改变了美国人口的分布。 不同胎龄的新生儿以及这些新生儿的出生体重分布。该项目将探索 这些成分变化可能是如何导致美国出生的婴儿出生体重下降的。 1990至2014年间，所有州的非西班牙裔黑人、非西班牙裔白人和拉丁裔母亲。该项目 将在官方国家生命统计中分析胎龄分布和出生体重分布 1990、1996、2002、2008和2014年的系统本地性文件。传统的人口统计技术和 生存模型将用于估计在特定地点出生的联合概率的变化。 通过特定的分娩方法(即剖腹产、引产或无干预的阴道分娩)孕周。 模拟技术将被用来说明非西班牙裔黑人、非西班牙裔美国人的出生体重分布 美国各州的西班牙裔白人和拉丁裔女性如果剖腹产率和 引产多年来一直保持不变。该项目的分析方法新颖，走得很好。 远远超出现有的分析，特别关注美国出生人口在以下方面的构成变化 出生方法、出生时间和出生体重。该项目的发现将对 人口学和公共卫生，并可能为产科做法和政策提供信息。

Project Summary Average birth weights in the United States declined substantially during the 1990s and 2000s and have not recovered to the birth weight levels prior to the declines. This project documents state-level birth weight trends among U.S. infants born to non-Hispanic black, non-Hispanic white, and Latina women between 1990 and 2014. The project investigates the extent to which increased rates of cesarean section deliveries (C-sections) and labor inductions were responsible for recent changes in U.S. birth weights. Existing research has thus far reported no link between birth weight declines in the United States and the increased use of C-sections and inductions. Futher, existing evidence suggests that changes in U.S. birth weight distributions have occurred across all weeks of gestational age. The anomalous declines in U.S. birth weights are therefore suspected to reflect sources of reduced fetal growth that have been independent of gestational age. However, analytic approaches from extant research have overlooked how the composition of births at gestational ages have changed as a result of rising use of C-sections and inductions. Increased uses of C-sections and inductions have not been random. Rather, they have disproportionately occurred at select gestational ages, which have dramatically shifted when U.S. births take place and how. These labor interventions often affect pregnancies that likely would have resulted in births taking place at older gestational ages and at higher birth weights if the interventions did not occur. The consequences of these changes have altered both the distribution of U.S. births across gestational ages as well as the birth weight distributions of these births. This project will explore how these compositional changes may be responsible for declines in birth weight among infants born to U.S. non-Hispanic black, non-Hispanic white, and Latina mothers in all states between 1990 and 2014. The project will analyze gestational age distributions and birth weight distributions in official National Vital Statistics Systems Natality files for years 1990, 1996, 2002, 2008, and 2014. Traditional demographic techniques and survival models will be used to estimate changes in the joint probabilities of births occurring at specific gestational ages via specific birthing methods (i.e., C-section, induction, or vaginal without intervention). Simulation techniques will be used to illustrate how birthweight distributions among non-Hispanic black, non- Hispanic white, and Latina women in all U.S. States would have changed if rates of C-section use and rates of induced labor had remained constant over the years. The analytic approach of the project is novel and goes well-beyond existing analyses by paying special attention to compositional changes in U.S. births in terms of birth method, birth timing, and birth weight. Findings from the project will contribute significantly to research in demography and public health, and potentially inform obstetric practices and policies.