利用世界卫生组织和美国国家卫生统计中心的标准确定了营养不良指标。
Malnutrition indicators were determined using WHO and NCHS growth standards.
根据美国国家卫生统计中心（National Center for Health Statistics）发布的数据，在1970年至2006年间，美国女性初次生育的平均年龄提高了3.6岁，达到了25岁。
The average age of U. S. women giving birth for the first time rose 3.6 years between 1970 and 2006 to 25 years, according to the National Center for Health Statistics.
据美国国家卫生统计中心（National Center for Health Statistics）3月份公布的数据，目前，美国的剖腹产率约为三分之一，较1998年的21%有所上升，成为发达国家中剖腹产率最高的国家之一。
Today, about a third of U. S. births are done by caesarean section, up from 21% in 1998, one of the highest of any developed country, the National Center for Health Statistics reported in March.
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