Clarke S C, Martin J A, Taffel S M
Stat Bull Metrop Insur Co. 1997 Jan-Mar;78(1):9-18.
In 1994 there were 218,466 births attended by midwives in the United States more than seven times the number in 1975 (29,413). The percent of all births attended by midwives rose from 0.9 percent in 1975 to 5.5 percent in 1994. The vast majority of midwife attended births were by certified nurse-midwives (CNMs) and occurred in hospitals. Births attended by other midwives comprised only 6 percent of all midwife-attended births (down 11 percent since-1989) and are becoming increasingly concentrated in out of hospital settings, particularly residences. Due in large part to population characteristics, the proportions of births attended by midwives varies markedly between states. The percentages range from 19 percent in New Mexico to less than 1 percent in Kansas Louisiana Missouri and Nebraska Mothers with midwife attended births in out of hospital settings generally had demographic and lifestyle characteristics that were lower risk for obstetric complications and poor birth outcomes compared with mothers with physician- or midwife attended births in hospitals. That is these mothers were more likely to be married older more educated having higher order births and were less likely to smoke and gain and adequate amount of weight during pregnancy. However women with midwife attended births regardless of type of midwife or birth setting were more likely to initiate prenatal care later in the pregnancy and have fewer overall visits than were women whose births were attended by physicians. Despite less prenatal care a smaller proportion of babies whose births were attended by midwives were preterm or were of low or very low birth weight.
1994年，美国有218,466例分娩由助产士接生，这一数字是1975年（29,413例）的七倍多。由助产士接生的分娩占所有分娩的比例从1975年的0.9%升至1994年的5.5%。绝大多数由助产士接生的分娩是由注册护士助产士（CNMs）完成的，且发生在医院。由其他助产士接生的分娩仅占所有助产士接生分娩的6%（自1989年以来下降了11%），并且越来越集中在医院外的场所，尤其是住所。在很大程度上由于人口特征，各州由助产士接生的分娩比例差异显著。比例范围从新墨西哥州的19%到堪萨斯州、路易斯安那州、密苏里州和内布拉斯加州的不到1%。与在医院由医生或助产士接生的母亲相比，在医院外场所由助产士接生的母亲通常具有较低的产科并发症和不良分娩结局风险的人口统计学和生活方式特征。也就是说，这些母亲更有可能已婚、年龄较大、受教育程度较高、生育多胞胎，并且在怀孕期间吸烟和体重增加适量的可能性较小。然而，无论助产士类型或分娩场所如何，由助产士接生的女性在孕期更晚开始产前护理，且总体就诊次数比由医生接生的女性少。尽管产前护理较少，但由助产士接生的婴儿中早产或低出生体重或极低出生体重的比例较小。
